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Table of Contents
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 10-Q

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the quarterly period ended September 30, 2025
or
☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the transition period from to
Name of Registrant, State of Incorporation, Address of Principal Executive Offices, Telephone Number, Commission File Number, IRS Employer Identification Number
ALLIANT ENERGY CORPORATION
(a Wisconsin Corporation)
4902 N. Biltmore Lane
Madison, Wisconsin 53718
Telephone (608) 458-3311
Commission File Number - 1-9894
IRS Employer Identification Number - 39-1380265
INTERSTATE POWER & LIGHT COMPANY
(an Iowa corporation)
Alliant Energy Tower
Cedar Rapids, Iowa 52401
Telephone (319) 786-4411
Commission File Number - 1-4117
IRS Employer Identification Number - 42-0331370
WISCONSIN POWER & LIGHT COMPANY
(a Wisconsin corporation)
4902 N. Biltmore Lane
Madison, Wisconsin 53718
Telephone (608) 458-3311
Commission File Number - 0-337
IRS Employer Identification Number - 39-0714890
This combined Form 10-Q is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company. Information contained in the Form 10-Q relating to Interstate Power and Light Company and Wisconsin Power and Light Company is filed by each such registrant on its own behalf. Each of Interstate Power and Light Company and Wisconsin Power and Light Company makes no representation as to information relating to registrants other than itself.
Securities registered pursuant to Section 12(b) of the Act:
Alliant Energy Corporation, Common Stock, $0.01 Par Value, Trading Symbol LNT, Nasdaq Global Select Market
Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.
Alliant Energy Corporation - Yes ☒ No ☐
Interstate Power and Light Company - Yes ☒ No ☐
Wisconsin Power and Light Company - Yes ☒ No ☐
Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).
Alliant Energy Corporation - Yes ☒ No ☐
Interstate Power and Light Company - Yes ☒ No ☐
Wisconsin Power and Light Company - Yes ☒ No ☐
Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.
Alliant Energy Corporation - Large Accelerated Filer ☒ Accelerated Filer ☐ Non-accelerated Filer ☐ Smaller Reporting Company ☐ Emerging Growth Company ☐
Interstate Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐
Wisconsin Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.
Alliant Energy Corporation ☐
Interstate Power and Light Company ☐
Wisconsin Power and Light Company ☐
Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).
Alliant Energy Corporation - Yes ☐ No ☒
Interstate Power and Light Company - Yes ☐ No ☒
Wisconsin Power and Light Company - Yes ☐ No ☒
Number of shares outstanding of each class of common stock as of September 30, 2025:
Alliant Energy Corporation, Common Stock, $0.01 par value, 257,053,689 shares outstanding
Interstate Power and Light Company, Common Stock, $2.50 par value, 13,370,788 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation)
Wisconsin Power and Light Company, Common Stock, $5 par value, 13,236,601 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation)

Table of Contents
TABLE OF CONTENTS

| Page
Definitions |
Forward-looking Statements | 1
Part I. Financial Information | 3
Item 1. Condensed Consolidated Financial Statements (Unaudited) | 3
Alliant Energy Corporation | 3
Interstate Power and Light Company | 6
Wisconsin Power and Light Company | 9
Combined Notes to Condensed Consolidated Financial Statements | 12
1. Summary of Significant Accounting Policies | 12
2. Regulatory Matters | 12
3. Property, Plant and Equipment | 13
4. Receivables | 13
5. Investments | 14
6. Common Equity | 14
7. Debt | 16
8. Revenues | 18
9. Income Taxes | 19
10. Benefit Plans | 20
1 1. Derivative Instruments | 21
1 2. Fair Value Measurements | 22
1 3. Commitments and Contingencies | 24
1 4. Segments of Business | 26
1 5. Related Parties | 27
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations | 28
Item 3. Quantitative and Qualitative Disclosures About Market Risk | 39
Item 4. Controls and Procedures | 39
Part II. Other Information | 39
Item 1. Legal Proceedings | 39
Item 1A. Risk Factors | 39
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds | 40
Item 5. Other Information | 40
Item 6. Exhibits | 40
Signatures | 41

DEFINITIONS
The following abbreviations or acronyms used in this report are defined below:

Abbreviation or Acronym | Definition | Abbreviation or Acronym | Definition
2024 Form 10-K | Combined Annual Report on Form 10-K filed by Alliant Energy, IPL and WPL for the year ended Dec. 31, 2024 | IPL | Interstate Power and Light Company
AEF | Alliant Energy Finance, LLC | IUC | Iowa Utilities Commission
Alliant Energy | Alliant Energy Corporation | MDA | Management’s Discussion and Analysis of Financial Condition and Results of Operations
ATC | American Transmission Company LLC | MISO | Midcontinent Independent System Operator, Inc.
ATC Holdings | Interest in American Transmission Company LLC and ATC Holdco LLC | MW | Megawatt
Corporate Services | Alliant Energy Corporate Services, Inc. | MWh | Megawatt-hour
Dth | Dekatherm | N/A | Not applicable
EPA | U.S. Environmental Protection Agency | Note(s) | Combined Notes to Condensed Consolidated Financial Statements
EPS | Earnings per weighted average common share | PSCW | Public Service Commission of Wisconsin
Financial Statements | Condensed Consolidated Financial Statements | U.S. | United States of America
FTR | Financial transmission right | West Riverside | West Riverside Energy Center and Solar Facility
GAAP | U.S. generally accepted accounting principles | WPL | Wisconsin Power and Light Company

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FORWARD-LOOKING STATEMENTS
Statements contained in this report that are not of historical fact are forward-looking statements intended to qualify for the safe harbors from liability established by the Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified as such because the statements include words such as “may,” “believe,” “expect,” “anticipate,” “plan,” “project,” “will,” “projections,” “estimate,” or other words of similar import. Similarly, statements that describe future financial performance or plans or strategies are forward-looking statements. Such forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those expressed in, or implied by, such statements. Some, but not all, of the risks and uncertainties of Alliant Energy, IPL and WPL that could materially affect actual results include:
•IPL’s and WPL’s ability to obtain adequate and timely rate relief to allow for, among other things, recovery of and/or the return on costs, including fuel costs, operating costs, transmission costs, capacity costs, costs of generation projects including such costs that are incurred prior to regulatory approval or exceed initial estimates, deferred expenditures, deferred tax assets, tax expense, interest expense, capital expenditures, marginal costs to service new customers, and remaining costs related to electric generating units (EGUs) that have been or may be permanently closed and certain other retired assets, environmental remediation costs, and decreases in sales volumes, as well as earning their authorized rates of return, payments to their parent of expected levels of dividends, the impact of rate design on current and potential customers and demand for energy in their service territories, and the ability to obtain regulatory approval with acceptable conditions for individual customer rates for large load growth customers;
•the impact of IPL’s retail electric base rate moratorium;
•the ability to obtain regulatory approval for constr uction projects with acceptable conditions;
•the ability to complete construction of generation and energy storage projects by planned in-service dates and within the cost targets set by regulators due to cost increases of and access to materials, equipment and commodities, which could result from tariffs, including previously exempted tariffs related to solar project materials and equipment from certain countries, duties or other assessments, inflation, labor issues or supply shortages, the ability to successfully resolve warranty issues or contract disputes and the ability to obtain adequate generator interconnection agreements to connect the new projects to MISO in a timely manner;
•weather effects on utility sales volumes and operations;
•the direct or indirect effects resulting from cybersecurity incidents or attacks on Alliant Energy, IPL, WPL, or their suppliers, contractors and partners, or responses to such incidents;
•the impact of customer- and third party-owned generation, including alternative electric suppliers and potential policy changes that may enable large customers to source behind-the-meter generation directly from third parties, in IPL’s and WPL’s service territories on system reliability, operating expenses and customers’ demand for electricity;
•economic conditions in IPL’s and WPL’s service territories, including the potential impacts of business or facility closures and tariffs;
•the ability and cost to provide sufficient generation and the ability of ITC Midwest LLC and ATC to provide sufficient transmission capacity for potential load growth timely, including significant new commercial or industrial customers, such as data centers;
•the ability of potential large load growth customers to timely construct new facilities, due to local or state regulatory actions, zoning or permitting actions, public opposition or other factors, as well as the resulting higher system load demand by expected levels and timeframes;
•the impact of energy efficiency, franchise retention and customer disconnects on sales volumes and operating income;
•the impact that price changes may have on IPL’s and WPL’s customers’ demand for electric and gas services and their ability to pay their bills;
•changes in the price of delivered natural gas, transmission, purchased electric energy, purchased electric capacity and delivered coal, particularly during elevated market prices, and any resulting changes to counterparty credit risk, due to shifts in supply and demand caused by market conditions, regulations and MISO’s seasonal resource adequacy process;
•the ability to achieve the expected level of tax benefits for renewable generation and energy storage projects based on tax guidelines, timely beginning of construction and in-service dates, sourcing permissible amounts of construction support from entities with ties to certain foreign countries, compliance with prevailing wage and apprenticeship requirements, project costs and the level of electricity output generated by qualifying generating facilities, and the ability to efficiently utilize the renewable generation and energy storage project tax benefits to achieve IPL’s authorized rate of return and for the benefit of IPL’s and WPL’s customers;
•federal and state regulatory or governmental actions, including the impact of legislation, Treasury regulations, executive orders, interpretations and guidance, and changes in public policy, including changes impacting renewable tax credits and siting generation and energy storage projects;
•the ability to utilize tax credits generated to date, and those that may be generated in the future, before they expire, as well as the ability to transfer tax credits that may be generated in the future at adequate pricing;
•the impacts of changes in the tax code, including tax rates, minimum tax rates, adjustments made to deferred tax assets and liabilities, and changes impacting the availability of and ability to transfer renewable tax credits, including preserving the qualification of any future tax credits;
•disruptions to ongoing operations and the supply of materials, services, equipment and commodities needed to continue to operate and maintain existing assets and to construct capital projects, which may result from geopolitical issues, tariffs, supplier manufacturing constraints, regulatory requirements, labor issues or transportation issues, and thus affect the ability to meet capacity requirements and result in increased capacity expense;
•inflation and higher interest rates;
•continued access to the capital markets on competitive terms and rates, and the actions of credit rating agencies;
•the future development of technologies related to electrification, and the ability to reliably store and manage electricity;
•employee workforce factors, including the ability to hire and retain employees with specialized skills, impacts from employee retirements, changes in key executives, ability to create desired corporate culture, collective bargaining agreements and negotiations, work stoppages or restructurings;

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Table of Contents
•disruptions in the supply and delivery of natural gas, purchased electricity and coal;
•changes to the creditworthiness of, or performance of obligations by, counterparties with which Alliant Energy, IPL and WPL have contractual arrangements, including large load growth customers, participants in the energy markets and fuel suppliers and transporters;
•the impact of penalties or third-party claims related to, or in connection with, a failure to maintain the security of personally identifiable information, including associated costs to notify affected persons and to mitigate their information security concerns;
•impacts that terrorist attacks may have on Alliant Energy’s, IPL’s and WPL’s operations and recovery of costs associated with restoration activities, or on the operations of Alliant Energy’s investments;
•changes to MISO’s resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements that may impact how and when new and existing generating facilities, including IPL’s and WPL’s additional solar generation, may be accredited with energy capacity, and may require IPL and WPL to adjust their current resource plans, to add resources to meet the requirements of MISO’s process, or procure capacity in the market whereby such costs might not be recovered in rates;
•any material post-closing payments related to any past asset divestitures, including the transfer of renewable tax credits, which could result from, among other things, indemnification agreements, warranties, guarantees or litigation;
•issues associated with environmental remediation and environmental compliance, including compliance with all current environmental and emissions laws, regulations and permits and future changes in environmental laws and regulations, including the Coal Combustion Residuals Rule, Cross-State Air Pollution Rule and federal, state or local regulations for emissions reductions, including greenhouse gases (GHG), from new and existing fossil-fueled EGUs under the Clean Air Act, and litigation associated with environmental requirements;
•increased pressure from customers, investors and other stakeholders to more rapidly reduce GHG emissions;
•the timely development of technologies, innovations and advancements to provide cost effective alternatives to traditional energy sources;
•the ability to defend against environmental claims brought by state and federal agencies, such as the EPA and state natural resources agencies, or third parties, such as the Sierra Club, and the impact on operating expenses of defending and resolving such claims;
•the direct or indirect effects resulting from breakdown or failure of equipment in the operation of electric and gas distribution systems, such as mechanical problems, disruptions in telecommunications, technological problems, and explosions or fires, and compliance with electric and gas transmission and distribution safety regulations, including regulations promulgated by the Pipeline and Hazardous Materials Safety Administration;
•issues related to the availability and operations of EGUs and energy storage facilities, including start-up risks, breakdown or failure of equipment, fires, availability of warranty coverage and successful resolution of warranty issues or contract disputes for equipment breakdowns or failures, performance below expected or contracted levels of output or efficiency, operator error, employee safety, transmission constraints, compliance with mandatory reliability standards and risks related to recovery of resulting incremental operating, capacity, fuel-related and capital costs through rates;
•impacts that excessive heat, excessive cold, storms, wildfires, or natural disasters may have on Alliant Energy’s, IPL’s and WPL’s operations and construction activities, and recovery of costs associated with restoration activities, or on the operations of Alliant Energy’s investments;
•Alliant Energy’s ability to sustain its dividend payout ratio goal;
•changes to costs of providing benefits and related funding requirements of pension and other postretirement benefits (OPEB) plans due to the market value of the assets that fund the plans, economic conditions, financial market performance, interest rates, timing and form of benefits payments, life expectancies and demographics;
•material changes in employee-related benefit and compensation costs, including settlement losses related to pension plans;
•risks associated with operation and ownership of non-utility holdings, including potential impairments;
•changes in technology that alter the channels through which customers buy or utilize Alliant Energy’s, IPL’s or WPL’s products and services;
•impacts on equity income from unconsolidated investments from changes in valuations of the assets held, as well as potential changes to ATC’s authorized return on equity;
•impacts of IPL’s future tax benefits from Iowa rate-making practices, including deductions for repairs expenditures and cost of removal obligations, allocation of mixed service costs and state depreciation, and recoverability of the associated regulatory assets from customers, when the differences reverse in future periods;
•current or future litigation, regulatory investigations, proceedings or inquiries;
•reputational damage from negative publicity, protests, fines, penalties and other negative consequences resulting in regulatory and/or legal actions;
•the direct or indirect effects resulting from pandemics;
•the effect of accounting standards issued periodically by standard-setting bodies;
•the ability to successfully complete tax audits and changes in tax accounting methods with no material impact on earnings and cash flows; and
•other factors listed in MDA and Risk Factors in Item 1A in the 2024 Form 10-K.
Alliant Energy, IPL and WPL each assume no obligation, and disclaim any duty, to update the forward-looking statements in this report, except as required by law.
Available Information. Alliant Energy routinely posts important information on its website and considers the Investors section of its website, www.alliantenergy.com/investors, a channel of distribution for material information. Information contained on Alliant Energy’s website is not incorporated herein by reference.

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PART I. FINANCIAL INFORMATION
ITEM 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)
ALLIANT ENERGY CORPORATION
CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

| For the Three Months |  | For the Nine Months
| Ended September 30, |  | Ended September 30,
| 2025 |  | 2024 |  | 2025 |  | 2024
| (in millions, except per share amounts)
Revenues: |  |  |  |  |  |  |
Electric utility | $1,124 |  | $999 |  | $2,828 |  | $2,579
Gas utility | 51 |  | 49 |  | 366 |  | 322
Other utility | 12 |  | 12 |  | 37 |  | 36
Non-utility | 23 |  | 21 |  | 67 |  | 68
Total revenues | 1,210 |  | 1,081 |  | 3,298 |  | 3,005
Operating expenses: |  |  |  |  |  |  |
Electric production fuel and purchased power | 239 |  | 192 |  | 564 |  | 493
Electric transmission service | 166 |  | 165 |  | 474 |  | 464
Cost of gas sold | 12 |  | 13 |  | 180 |  | 152
Other operation and maintenance: |  |  |  |  |  |  |
Asset valuation charge for IPL’s Lansing Generating Station | — |  | — |  | — |  | 60
Other | 204 |  | 174 |  | 530 |  | 510
Depreciation and amortization | 211 |  | 195 |  | 631 |  | 571
Taxes other than income taxes | 29 |  | 29 |  | 91 |  | 90
Total operating expenses | 861 |  | 768 |  | 2,470 |  | 2,340
Operating income | 349 |  | 313 |  | 828 |  | 665
Other (income) and deductions: |  |  |  |  |  |  |
Interest expense | 128 |  | 114 |  | 372 |  | 329
Equity income from unconsolidated investments, net | (18) |  | (14) |  | (41) |  | (44)
Allowance for funds used during construction | (24) |  | (20) |  | (65) |  | (58)
Other | — |  | — |  | 3 |  | 2
Total other (income) and deductions | 86 |  | 80 |  | 269 |  | 229
Income before income taxes | 263 |  | 233 |  | 559 |  | 436
Income tax benefit | (18) |  | (62) |  | (109) |  | (104)
Net income attributable to Alliant Energy common shareowners | $281 |  | $295 |  | $668 |  | $540
Weighted average number of common shares outstanding: |  |  |  |  |  |  |
Basic | 257.0 |  | 256.6 |  | 256.9 |  | 256.4
Diluted | 257.8 |  | 256.9 |  | 257.5 |  | 256.7
Earnings per weighted average common share attributable to Alliant Energy common shareowners: |  |  |  |  |  |  |
Basic | $1.09 |  | $1.15 |  | $2.60 |  | $2.11
Diluted | $1.09 |  | $1.15 |  | $2.59 |  | $2.10

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION
CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

| September 30, 2025 |  | December 31, 2024
| (in millions, except per share and share amounts)
ASSETS |  |  |
Current assets: |  |  |
Cash and cash equivalents | $503 |  | $81
Short-term investments | 250 |  | —
Accounts receivable, less allowance for expected credit losses | 485 |  | 427
Production fuel, at weighted average cost | 37 |  | 54
Gas stored underground, at weighted average cost | 55 |  | 55
Materials and supplies, at weighted average cost | 189 |  | 186
Regulatory assets | 132 |  | 210
Other | 193 |  | 171
Total current assets | 1,844 |  | 1,184
Property, plant and equipment, net | 19,813 |  | 18,701
Investments: |  |  |
ATC Holdings | 459 |  | 415
Other | 230 |  | 224
Total investments | 689 |  | 639
Other assets: |  |  |
Regulatory assets | 2,171 |  | 2,064
Deferred charges and other | 110 |  | 126
Total other assets | 2,281 |  | 2,190
Total assets | $24,627 |  | $22,714

LIABILITIES AND EQUITY |  |  |
Current liabilities: |  |  |
Current maturities of long-term debt | $1,074 |  | $1,171
Commercial paper | 192 |  | 558
Accounts payable | 550 |  | 532
Regulatory liabilities | 58 |  | 69
Other | 360 |  | 385
Total current liabilities | 2,234 |  | 2,715
Long-term debt, net (excluding current portion) | 10,655 |  | 8,677
Other liabilities: |  |  |
Deferred tax liabilities | 2,187 |  | 2,188
Regulatory liabilities | 1,076 |  | 959
Pension and other benefit obligations | 197 |  | 224
Other | 971 |  | 947
Total other liabilities | 4,431 |  | 4,318
Commitments and contingencies (Note 1 3) |  |  |
Equity: |  |  |
Alliant Energy Corporation common equity: |  |  |
Common stock - $0.01 par value - 480,000,000 shares authorized; 257,053,689 and 256,690,222 shares outstanding | 3 |  | 3
Additional paid-in capital | 3,087 |  | 3,060
Retained earnings | 4,231 |  | 3,954
Accumulated other comprehensive income | — |  | 1
Shares in deferred compensation trust - 359,483 and 372,116 shares at a weighted average cost of $38.39 and $36.56 per share | (14) |  | (14)
Total Alliant Energy Corporation common equity | 7,307 |  | 7,004
Total liabilities and equity | $24,627 |  | $22,714

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

| For the Nine Months
| Ended September 30,
| 2025 |  | 2024
| (in millions)
Cash flows from operating activities: |  |  |
Net income | $668 |  | $540
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |
Depreciation and amortization | 631 |  | 571
Deferred tax benefit and tax credits | (125) |  | (103)
Asset valuation charge for IPL’s Lansing Generating Station | — |  | 60
Other | 2 |  | (9)
Other changes in assets and liabilities: |  |  |
Accounts receivable | (391) |  | (388)
Regulatory liabilities | 107 |  | (67)
Deferred income taxes (a) | 101 |  | 222
Other | (93) |  | 87
Net cash flows from operating activities | 900 |  | 913
Cash flows used for investing activities: |  |  |
Construction and acquisition expenditures: |  |  |
Utility business | (1,487) |  | (1,280)
Other | (161) |  | (154)
Cash receipts on sold receivables | 332 |  | 399
Purchases of short-term investments | (250) |  | —
Proceeds from sales of partial ownership interests in West Riverside | — |  | 123
Other | (39) |  | (28)
Net cash flows used for investing activities | (1,605) |  | (940)
Cash flows from financing activities: |  |  |
Common stock dividends | (391) |  | (369)
Proceeds from issuance of long-term debt | 2,174 |  | 1,613
Payments to retire long-term debt | (300) |  | (305)
Net change in commercial paper | (366) |  | (145)
Other | 10 |  | —
Net cash flows from financing activities | 1,127 |  | 794
Net increase in cash, cash equivalents and restricted cash | 422 |  | 767
Cash, cash equivalents and restricted cash at beginning of period | 81 |  | 63
Cash, cash equivalents and restricted cash at end of period | $503 |  | $830
Supplemental cash flows information: |  |  |
Cash (paid) received during the period for: |  |  |
Interest | ($373) |  | ($326)
Income taxes, net (a) | $108 |  | $158
Significant non-cash investing and financing activities: |  |  |
Accrued capital expenditures | $246 |  | $194
Beneficial interest obtained in exchange for securitized accounts receivable | $231 |  | $212

(a)2025 and 2024 include $117 million and $172 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.
Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

| For the Three Months |  | For the Nine Months
| Ended September 30, |  | Ended September 30,
| 2025 |  | 2024 |  | 2025 |  | 2024
| (in millions)
Revenues: |  |  |  |  |  |  |
Electric utility | $608 |  | $523 |  | $1,455 |  | $1,318
Gas utility | 27 |  | 27 |  | 185 |  | 175
Steam and other | 12 |  | 11 |  | 36 |  | 34
Total revenues | 647 |  | 561 |  | 1,676 |  | 1,527
Operating expenses: |  |  |  |  |  |  |
Electric production fuel and purchased power | 106 |  | 79 |  | 213 |  | 195
Electric transmission service | 115 |  | 115 |  | 322 |  | 317
Cost of gas sold | 7 |  | 8 |  | 89 |  | 85
Other operation and maintenance: |  |  |  |  |  |  |
Asset valuation charge for IPL’s Lansing Generating Station | — |  | — |  | — |  | 60
Other | 108 |  | 96 |  | 275 |  | 281
Depreciation and amortization | 116 |  | 100 |  | 346 |  | 294
Taxes other than income taxes | 15 |  | 14 |  | 44 |  | 45
Total operating expenses | 467 |  | 412 |  | 1,289 |  | 1,277
Operating income | 180 |  | 149 |  | 387 |  | 250
Other (income) and deductions: |  |  |  |  |  |  |
Interest expense | 54 |  | 44 |  | 154 |  | 128
Allowance for funds used during construction | (15) |  | (13) |  | (37) |  | (34)
Other | (3) |  | (4) |  | (6) |  | (4)
Total other (income) and deductions | 36 |  | 27 |  | 111 |  | 90
Income before income taxes | 144 |  | 122 |  | 276 |  | 160
Income tax benefit | (21) |  | (68) |  | (98) |  | (112)
Net income | $165 |  | $190 |  | $374 |  | $272

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.
Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

| September 30, 2025 |  | December 31, 2024
| (in millions, except per share and share amounts)
ASSETS |  |  |
Current assets: |  |  |
Cash and cash equivalents | $209 |  | $29
Accounts receivable, less allowance for expected credit losses | 252 |  | 192
Production fuel, at weighted average cost | 16 |  | 30
Gas stored underground, at weighted average cost | 26 |  | 25
Materials and supplies, at weighted average cost | 111 |  | 113
Regulatory assets | 68 |  | 77
Other | 58 |  | 43
Total current assets | 740 |  | 509
Property, plant and equipment, net | 10,083 |  | 9,336
Other assets: |  |  |
Regulatory assets | 1,564 |  | 1,509
Deferred charges and other | 46 |  | 53
Total other assets | 1,610 |  | 1,562
Total assets | $12,433 |  | $11,407

LIABILITIES AND EQUITY |  |  |
Current liabilities: |  |  |
Current maturities of long-term debt | $— |  | $300
Commercial paper | — |  | 50
Accounts payable | 289 |  | 263
Accounts payable to associated companies | 52 |  | 47
Accrued taxes | 74 |  | 77
Accrued interest | 49 |  | 48
Regulatory liabilities | 39 |  | 54
Other | 78 |  | 89
Total current liabilities | 581 |  | 928
Long-term debt, net (excluding current portion) | 4,679 |  | 3,790
Other liabilities: |  |  |
Deferred tax liabilities | 1,235 |  | 1,179
Regulatory liabilities | 519 |  | 492
Pension and other benefit obligations | 42 |  | 46
Other | 527 |  | 511
Total other liabilities | 2,323 |  | 2,228
Commitments and contingencies (Note 1 3) |  |  |
Equity: |  |  |
Interstate Power and Light Company common equity: |  |  |
Common stock - $2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding | 33 |  | 33
Additional paid-in capital | 3,497 |  | 3,212
Retained earnings | 1,320 |  | 1,216
Total Interstate Power and Light Company common equity | 4,850 |  | 4,461
Total liabilities and equity | $12,433 |  | $11,407

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

| For the Nine Months
| Ended September 30,
| 2025 |  | 2024
| (in millions)
Cash flows from operating activities: |  |  |
Net income | $374 |  | $272
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |
Depreciation and amortization | 346 |  | 294
Deferred tax benefit and tax credits | (81) |  | (64)
Asset valuation charge for IPL’s Lansing Generating Station | — |  | 60
Other | (16) |  | (1)
Other changes in assets and liabilities: |  |  |
Accounts receivable | (392) |  | (392)
Regulatory assets | (72) |  | (36)
Regulatory liabilities | 11 |  | (65)
Deferred income taxes (a) | 134 |  | 166
Other | (15) |  | (3)
Net cash flows from operating activities | 289 |  | 231
Cash flows used for investing activities: |  |  |
Construction and acquisition expenditures | (976) |  | (702)
Cash receipts on sold receivables | 332 |  | 399
Other | (16) |  | (29)
Net cash flows used for investing activities | (660) |  | (332)
Cash flows from financing activities: |  |  |
Common stock dividends | (270) |  | (151)
Capital contributions from parent | 285 |  | 325
Proceeds from issuance of long-term debt | 888 |  | 643
Payments to retire long-term debt | (300) |  | —
Net change in commercial paper | (50) |  | —
Other | (2) |  | (13)
Net cash flows from financing activities | 551 |  | 804
Net increase in cash, cash equivalents and restricted cash | 180 |  | 703
Cash, cash equivalents and restricted cash at beginning of period | 29 |  | 53
Cash, cash equivalents and restricted cash at end of period | $209 |  | $756
Supplemental cash flows information: |  |  |
Cash (paid) received during the period for: |  |  |
Interest | ($153) |  | ($122)
Income taxes, net (a) | $94 |  | $114
Significant non-cash investing and financing activities: |  |  |
Accrued capital expenditures | $152 |  | $120
Beneficial interest obtained in exchange for securitized accounts receivable | $231 |  | $212

(a)2025 and 2024 include $90 million and $89 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.
Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

| For the Three Months |  | For the Nine Months
| Ended September 30, |  | Ended September 30,
| 2025 |  | 2024 |  | 2025 |  | 2024
| (in millions)
Revenues: |  |  |  |  |  |  |
Electric utility | $516 |  | $476 |  | $1,373 |  | $1,261
Gas utility | 24 |  | 22 |  | 181 |  | 147
Other | — |  | 1 |  | 1 |  | 2
Total revenues | 540 |  | 499 |  | 1,555 |  | 1,410
Operating expenses: |  |  |  |  |  |  |
Electric production fuel and purchased power | 133 |  | 112 |  | 351 |  | 298
Electric transmission service | 51 |  | 49 |  | 152 |  | 148
Cost of gas sold | 5 |  | 5 |  | 91 |  | 67
Other operation and maintenance | 84 |  | 72 |  | 222 |  | 200
Depreciation and amortization | 92 |  | 91 |  | 275 |  | 269
Taxes other than income taxes | 13 |  | 14 |  | 42 |  | 41
Total operating expenses | 378 |  | 343 |  | 1,133 |  | 1,023
Operating income | 162 |  | 156 |  | 422 |  | 387
Other (income) and deductions: |  |  |  |  |  |  |
Interest expense | 43 |  | 42 |  | 129 |  | 124
Allowance for funds used during construction | (9) |  | (7) |  | (28) |  | (24)
Other | 4 |  | 3 |  | 9 |  | 4
Total other (income) and deductions | 38 |  | 38 |  | 110 |  | 104
Income before income taxes | 124 |  | 118 |  | 312 |  | 283
Income tax expense (benefit) | 1 |  | 4 |  | (9) |  | 13
Net income | $123 |  | $114 |  | $321 |  | $270

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented.
Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

| September 30, 2025 |  | December 31, 2024
| (in millions, except per share and share amounts)
ASSETS |  |  |
Current assets: |  |  |
Cash and cash equivalents | $11 |  | $51
Accounts receivable, less allowance for expected credit losses | 218 |  | 220
Production fuel, at weighted average cost | 21 |  | 24
Gas stored underground, at weighted average cost | 29 |  | 30
Materials and supplies, at weighted average cost | 72 |  | 69
Regulatory assets | 64 |  | 133
Prepaid gross receipts tax | 38 |  | 51
Other | 53 |  | 57
Total current assets | 506 |  | 635
Property, plant and equipment, net | 9,166 |  | 8,861
Other assets: |  |  |
Regulatory assets | 607 |  | 555
Deferred charges and other | 52 |  | 55
Total other assets | 659 |  | 610
Total assets | $10,331 |  | $10,106

LIABILITIES AND EQUITY |  |  |
Current liabilities: |  |  |
Commercial paper | $192 |  | $183
Accounts payable | 189 |  | 209
Accrued interest | 41 |  | 44
Regulatory liabilities | 19 |  | 15
Other | 86 |  | 94
Total current liabilities | 527 |  | 545
Long-term debt, net | 3,372 |  | 3,370
Other liabilities: |  |  |
Deferred tax liabilities | 786 |  | 865
Regulatory liabilities | 557 |  | 467
Pension and other benefit obligations | 85 |  | 102
Other | 665 |  | 656
Total other liabilities | 2,093 |  | 2,090
Commitments and contingencies (Note 1 3) |  |  |
Equity: |  |  |
Wisconsin Power and Light Company common equity: |  |  |
Common stock - $5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding | 66 |  | 66
Additional paid-in capital | 2,613 |  | 2,533
Retained earnings | 1,660 |  | 1,502
Total Wisconsin Power and Light Company common equity | 4,339 |  | 4,101
Total liabilities and equity | $10,331 |  | $10,106

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

| For the Nine Months
| Ended September 30,
| 2025 |  | 2024
| (in millions)
Cash flows from operating activities: |  |  |
Net income | $321 |  | $270
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |
Depreciation and amortization | 275 |  | 269
Deferred tax benefit and tax credits | (60) |  | (45)
Other | (2) |  | (2)
Other changes in assets and liabilities: |  |  |
Regulatory assets | 24 |  | 62
Regulatory liabilities | 96 |  | (1)
Deferred income taxes (a) | (38) |  | 60
Other | (43) |  | 38
Net cash flows from operating activities | 573 |  | 651
Cash flows used for investing activities: |  |  |
Construction and acquisition expenditures | (511) |  | (578)
Proceeds from sales of partial ownership interests in West Riverside | — |  | 123
Other | (19) |  | (9)
Net cash flows used for investing activities | (530) |  | (464)
Cash flows used for financing activities: |  |  |
Common stock dividends | (163) |  | (147)
Capital contributions from parent | 80 |  | 55
Proceeds from issuance of long-term debt | — |  | 297
Net change in commercial paper | 9 |  | (318)
Other | (9) |  | (12)
Net cash flows used for financing activities | (83) |  | (125)
Net increase (decrease) in cash, cash equivalents and restricted cash | (40) |  | 62
Cash, cash equivalents and restricted cash at beginning of period | 51 |  | 7
Cash, cash equivalents and restricted cash at end of period | $11 |  | $69
Supplemental cash flows information: |  |  |
Cash (paid) received during the period for: |  |  |
Interest | ($136) |  | ($123)
Income taxes, net (a) | ($7) |  | $36
Significant non-cash investing and financing activities: |  |  |
Accrued capital expenditures | $89 |  | $68

(a)2025 and 2024 include $27 million and $83 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.
Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION
INTERSTATE POWER AND LIGHT COMPANY
WISCONSIN POWER AND LIGHT COMPANY
COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)
NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2024 Form 10-K.
In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2025 are not necessarily indicative of results that may be expected for the year ending December 31, 2025.
A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.
NOTE 1(b) Cash and Cash Equivalents - At September 30, 2025, cash and cash equivalents included money market fund investments of $477 million and $194 million for Alliant Energy and IPL, respectively, with weighted average interest rates of 4%.
Note 1(c) Short-term Investments - Short-term investments include investments that have original maturities of greater than 90 days and remaining maturities of less than one year, and are convertible to known amounts of cash. At September 30, 2025, short-term investments included time deposits of $250 million for Alliant Energy, with weighted average interest rates of 4%.
NOTE 1(d) Asset Retirement Obligations (AROs) - In the second quarter of 2024, substantially due to the enactment of the revised Coal Combustion Residuals Rule, Alliant Energy and IPL recorded a pre-tax non-cash charge of $20 million to “Other operation and maintenance” in their income statements for the nine months ended September 30, 2024 for the AROs allocated to IPL’s steam business for its Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews.
NOTE 2. REGULATORY MATTERS
Regulatory Assets and Regulatory Liabilities -
Regulatory assets were comprised of the following items (in millions):

| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Tax-related | $1,069 |  | $989 |  | $932 |  | $870 |  | $137 |  | $119
AROs | 441 |  | 401 |  | 304 |  | 281 |  | 137 |  | 120
Pension and OPEB costs | 301 |  | 315 |  | 151 |  | 157 |  | 150 |  | 158
Assets retired early | 162 |  | 180 |  | 153 |  | 168 |  | 9 |  | 12
Non-service pension and OPEB costs | 55 |  | 51 |  | 20 |  | 19 |  | 35 |  | 32
Derivatives | 51 |  | 60 |  | 12 |  | 15 |  | 39 |  | 45
WPL’s Western Wisconsin gas distribution expansion investments | 40 |  | 42 |  | — |  | — |  | 40 |  | 42
Commodity cost recovery | 33 |  | 68 |  | 8 |  | 2 |  | 25 |  | 66
Other | 151 |  | 168 |  | 52 |  | 74 |  | 99 |  | 94
| $2,303 |  | $2,274 |  | $1,632 |  | $1,586 |  | $671 |  | $688

Assets retired early - IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period included a return of the remaining net book value of Lansing, but did not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value was no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024.

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Regulatory liabilities were comprised of the following items (in millions):

| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Tax-related | $658 |  | $582 |  | $301 |  | $286 |  | $357 |  | $296
Cost of removal obligations | 351 |  | 347 |  | 206 |  | 205 |  | 145 |  | 142
Derivatives | 49 |  | 53 |  | 25 |  | 29 |  | 24 |  | 24
Other | 76 |  | 46 |  | 26 |  | 26 |  | 50 |  | 20
| $1,134 |  | $1,028 |  | $558 |  | $546 |  | $576 |  | $482

Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from investment tax credits recognized by WPL for certain energy storage facilities in 2025.
NOTE 3. PROPERTY, PLANT AND EQUIPMENT
Construction costs associated with WPL’s approximately 1,100 MW of new solar generation exceeded the construction cost estimates previously approved by the PSCW by approximately $205 million. In September 2025, WPL filed a settlement agreement with the PSCW for the 2026/2027 forward-looking Test Period. In November 2025, the PSCW issued an oral decision approving the settlement, which includes a full return of and on these solar generation construction costs from WPL’s retail electric customers. As a result, Alliant Energy and WPL concluded that there was not a probable disallowance of the higher rate base amounts as of September 30, 2025. A written order from the PSCW is currently expected by the end of 2025.
As of December 31, 2024, WPL planned to cease coal operations at Columbia Units 1 and 2 by the end of 2029, and Alliant Energy and WPL concluded that Columbia Units 1 and 2 met the criteria to be considered probable of abandonment. WPL currently plans to continue coal operations at Columbia Units 1 and 2 at least through 2029 as well as evaluate the potential conversion of Columbia Unit 1 and/or Unit 2 to natural gas. As a result, as of September 30, 2025, Alliant Energy and WPL concluded that Columbia Units 1 and 2 (net book value of $398 million) no longer meet the criteria to be considered probable of abandonment.
NOTE 4. RECEIVABLES
Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. Effective September 2025, the limit on cash proceeds under the Receivables Agreement was changed to $5 million. As of September 30, 2025, IPL had $4 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
Maximum outstanding aggregate cash proceeds | $110 |  | $52 |  | $110 |  | $110
Average outstanding aggregate cash proceeds | 28 |  | 7 |  | 65 |  | 34

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

| September 30, 2025 |  | December 31, 2024
Customer accounts receivable | $166 |  | $137
Unbilled utility revenues | 79 |  | 108
Other receivables | 1 |  | —
Receivables sold to third party | 246 |  | 245
Less: cash proceeds | 1 |  | 70
Deferred proceeds | 245 |  | 175
Less: allowance for expected credit losses | 14 |  | 12
Fair value of deferred proceeds | $231 |  | $163

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As of September 30, 2025, outstanding receivables past due under the Receivables Agreement were $19 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
Collections | $681 |  | $565 |  | $1,732 |  | $1,578
Write-offs, net of recoveries | 5 |  | 4 |  | 9 |  | 9

NOTE 5. INVESTMENTS
Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
ATC Holdings | ($15) |  | ($13) |  | ($43) |  | ($38)
Non-utility wind farm in Oklahoma | (2) |  | (2) |  | (6) |  | (5)
Corporate venture investments | (1) |  | 2 |  | 10 |  | 1
Other | — |  | (1) |  | (2) |  | (2)
| ($18) |  | ($14) |  | ($41) |  | ($44)

NOTE 6. COMMON EQUITY
Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2025 | 256,690,222 |
Shareowner Direct Plan | 277,090 |
Equity-based compensation plans | 86,377 |
Shares outstanding, September 30, 2025 | 257,053,689 |

At-the-Market Offering Program - In May 2025, Alliant Energy filed a prospectus supplement and executed a related distribution agreement, under which it may sell up to $1.3 billion in aggregate of its common stock through 2028 through an at-the-market offering program that includes an equity forward sales component. Alliant Energy expects to use proceeds from the issuance of common stock for general corporate purposes.
Alliant Energy entered into forward sale agreements under its at-the-market offering program with various counterparties who, for the three and nine months ended September 30, 2025, borrowed and sold an aggregate of 7,851,080 and 10,764,103 shares of Alliant Energy common stock at an aggregate gross sales price of $508 million and $686 million, including approximately $4 million and $5 million in commissions, respectively, to the counterparties payable by Alliant Energy when the forward sale agreements are settled. Alliant Energy has not yet received any proceeds from this program and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy currently expects to settle the forward sale agreements in 2026 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of September 30, 2025, the weighted-average forward price, net of commissions, was $63.46 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of September 30, 2025, Alliant Energy could have settled all of its outstanding forward sale agreements under the at-the-market offering program with physical delivery of 10,764,103 shares of Alliant Energy common stock to the counterparties in exchange for cash of $683 million.
Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. As of September 30, 2025, 199,923 incremental shares were included in the calculation of diluted EPS related to the securities under the forward sale agreements.

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Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy |  |  |  |  |  |  | Accumulated |  | Shares in |  |  |  |
|  |  | Additional |  |  |  | Other |  | Deferred |  |  |  | Total
| Common |  | Paid-In |  | Retained |  | Comprehensive |  | Compensation |  |  |  | Common
| Stock |  | Capital |  | Earnings |  | Income (Loss) |  | Trust |  |  |  | Equity
Three Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2025 | $3 |  | $3,075 |  | $4,080 |  | $— |  | ($13) |  |  |  | $7,145
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 281 |  |  |  |  |  |  |  | 281
Common stock dividends ($0.5075 per share) |  |  |  |  | (130) |  |  |  |  |  |  |  | (130)
Shareowner Direct Plan issuances |  |  | 6 |  |  |  |  |  |  |  |  |  | 6
Equity-based compensation plans and other |  |  | 6 |  |  |  |  |  | (1) |  |  |  | 5
Ending balance, September 30, 2025 | $3 |  | $3,087 |  | $4,231 |  | $— |  | ($14) |  |  |  | $7,307
Three Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2024 | $3 |  | $3,042 |  | $3,755 |  | $3 |  | ($12) |  |  |  | $6,791
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 295 |  |  |  |  |  |  |  | 295
Common stock dividends ($0.48 per share) |  |  |  |  | (123) |  |  |  |  |  |  |  | (123)
Shareowner Direct Plan issuances |  |  | 6 |  |  |  |  |  |  |  |  |  | 6
Equity-based compensation plans and other |  |  | 4 |  |  |  |  |  | (1) |  |  |  | 3
Other comprehensive loss, net of tax |  |  |  |  |  |  | (4) |  |  |  |  |  | (4)
Ending balance, September 30, 2024 | $3 |  | $3,052 |  | $3,927 |  | ($1) |  | ($13) |  |  |  | $6,968

Alliant Energy |  |  |  |  |  |  | Accumulated |  | Shares in |  |  |  |
|  |  | Additional |  |  |  | Other |  | Deferred |  |  |  | Total
| Common |  | Paid-In |  | Retained |  | Comprehensive |  | Compensation |  |  |  | Common
| Stock |  | Capital |  | Earnings |  | Income (Loss) |  | Trust |  |  |  | Equity
Nine Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2024 | $3 |  | $3,060 |  | $3,954 |  | $1 |  | ($14) |  |  |  | $7,004
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 668 |  |  |  |  |  |  |  | 668
Common stock dividends ($1.5225 per share) |  |  |  |  | (391) |  |  |  |  |  |  |  | (391)
Shareowner Direct Plan issuances |  |  | 18 |  |  |  |  |  |  |  |  |  | 18
Equity-based compensation plans and other |  |  | 9 |  |  |  |  |  |  |  |  |  | 9
Other comprehensive loss, net of tax |  |  |  |  |  |  | (1) |  |  |  |  |  | (1)
Ending balance, September 30, 2025 | $3 |  | $3,087 |  | $4,231 |  | $— |  | ($14) |  |  |  | $7,307
Nine Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2023 | $3 |  | $3,030 |  | $3,756 |  | $1 |  | ($13) |  |  |  | $6,777
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 540 |  |  |  |  |  |  |  | 540
Common stock dividends ($1.44 per share) |  |  |  |  | (369) |  |  |  |  |  |  |  | (369)
Shareowner Direct Plan issuances |  |  | 18 |  |  |  |  |  |  |  |  |  | 18
Equity-based compensation plans and other |  |  | 4 |  |  |  |  |  |  |  |  |  | 4
Other comprehensive loss, net of tax |  |  |  |  |  |  | (2) |  |  |  |  |  | (2)
Ending balance, September 30, 2024 | $3 |  | $3,052 |  | $3,927 |  | ($1) |  | ($13) |  |  |  | $6,968

IPL |  |  | Additional |  |  |  |  |  | Total
| Common |  | Paid-In |  | Retained |  |  |  | Common
| Stock |  | Capital |  | Earnings |  |  |  | Equity
Three Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2025 | $33 |  | $3,357 |  | $1,245 |  |  |  | $4,635
Net income |  |  |  |  | 165 |  |  |  | 165
Common stock dividends |  |  |  |  | (90) |  |  |  | (90)
Capital contributions from parent |  |  | 140 |  |  |  |  |  | 140
Ending balance, September 30, 2025 | $33 |  | $3,497 |  | $1,320 |  |  |  | $4,850
Three Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2024 | $33 |  | $3,012 |  | $1,035 |  |  |  | $4,080
Net income |  |  |  |  | 190 |  |  |  | 190
Common stock dividends |  |  |  |  | (50) |  |  |  | (50)
Capital contributions from parent |  |  | 200 |  |  |  |  |  | 200
Ending balance, September 30, 2024 | $33 |  | $3,212 |  | $1,175 |  |  |  | $4,420

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IPL |  |  | Additional |  |  |  |  |  | Total
| Common |  | Paid-In |  | Retained |  |  |  | Common
| Stock |  | Capital |  | Earnings |  |  |  | Equity
Nine Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2024 | $33 |  | $3,212 |  | $1,216 |  |  |  | $4,461
Net income |  |  |  |  | 374 |  |  |  | 374
Common stock dividends |  |  |  |  | (270) |  |  |  | (270)
Capital contributions from parent |  |  | 285 |  |  |  |  |  | 285
Ending balance, September 30, 2025 | $33 |  | $3,497 |  | $1,320 |  |  |  | $4,850
Nine Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2023 | $33 |  | $2,887 |  | $1,054 |  |  |  | $3,974
Net income |  |  |  |  | 272 |  |  |  | 272
Common stock dividends |  |  |  |  | (151) |  |  |  | (151)
Capital contributions from parent |  |  | 325 |  |  |  |  |  | 325
Ending balance, September 30, 2024 | $33 |  | $3,212 |  | $1,175 |  |  |  | $4,420

WPL |  |  | Additional |  |  |  |  |  | Total
| Common |  | Paid-In |  | Retained |  |  |  | Common
| Stock |  | Capital |  | Earnings |  |  |  | Equity
Three Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2025 | $66 |  | $2,533 |  | $1,581 |  |  |  | $4,180
Net income |  |  |  |  | 123 |  |  |  | 123
Common stock dividends |  |  |  |  | (44) |  |  |  | (44)
Capital contributions from parent |  |  | 80 |  |  |  |  |  | 80
Ending balance, September 30, 2025 | $66 |  | $2,613 |  | $1,660 |  |  |  | $4,339
Three Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |
Beginning balance, June 30, 2024 | $66 |  | $2,533 |  | $1,411 |  |  |  | $4,010
Net income |  |  |  |  | 114 |  |  |  | 114
Common stock dividends |  |  |  |  | (49) |  |  |  | (49)
Ending balance, September 30, 2024 | $66 |  | $2,533 |  | $1,476 |  |  |  | $4,075

WPL |  |  | Additional |  |  |  |  |  | Total
| Common |  | Paid-In |  | Retained |  |  |  | Common
| Stock |  | Capital |  | Earnings |  |  |  | Equity
Nine Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2024 | $66 |  | $2,533 |  | $1,502 |  |  |  | $4,101
Net income |  |  |  |  | 321 |  |  |  | 321
Common stock dividends |  |  |  |  | (163) |  |  |  | (163)
Capital contributions from parent |  |  | 80 |  |  |  |  |  | 80
Ending balance, September 30, 2025 | $66 |  | $2,613 |  | $1,660 |  |  |  | $4,339
Nine Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2023 | $66 |  | $2,478 |  | $1,353 |  |  |  | $3,897
Net income |  |  |  |  | 270 |  |  |  | 270
Common stock dividends |  |  |  |  | (147) |  |  |  | (147)
Capital contributions from parent |  |  | 55 |  |  |  |  |  | 55
Ending balance, September 30, 2024 | $66 |  | $2,533 |  | $1,476 |  |  |  | $4,075

NOTE 7. DEBT
NOTE 7(a) Short-term Debt - In March 2025, Alliant Energy, IPL and WPL reallocated credit facility capacity amounts to $550 million for Alliant Energy at the parent company level, $350 million for IPL and $400 million for WPL, within the $1.3 billion total commitment. Information regarding commercial paper and borrowings under the single credit facility classified as short-term debt was as follows (dollars in millions):

September 30, 2025 | Alliant Energy |  | IPL |  | WPL
Amount outstanding | $192 |  | $— |  | $192
Weighted average interest rates | 4.3% |  | N/A |  | 4.3%
Available credit facility capacity | $1,108 |  | $350 |  | $208

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| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Maximum amount outstanding (based on daily outstanding balances) | $372 |  | $330 |  | $78 |  | $— |  | $297 |  | $—
Average amount outstanding (based on daily outstanding balances) | $263 |  | $197 |  | $9 |  | $— |  | $177 |  | $—
Weighted average interest rates | 4.5% |  | 5.4% |  | 4.6% |  | N/A |  | 4.5% |  | N/A
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $741 |  | $632 |  | $141 |  | $19 |  | $297 |  | $390
Average amount outstanding (based on daily outstanding balances) | $417 |  | $320 |  | $32 |  | $1 |  | $187 |  | $87
Weighted average interest rates | 4.6% |  | 5.5% |  | 4.6% |  | 5.5% |  | 4.5% |  | 5.5%

NOTE 7(b) Long-term Debt - In March 2025, AEF entered into a $300 million variable rate (5% as of September 30, 2025) term loan credit agreement (with Alliant Energy as guarantor), which expires in March 2026. This term loan credit agreement amended and restated the term loan credit agreement that expired in March 2025, and retired the $300 million variable rate term loan set forth therein, which was classified as a non-cash financing activity. AEF’s restated term loan credit agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $100 million.
In May 2025, IPL issued $600 million of 5.6% senior debentures due 2035. The net proceeds from this issuance were used for the retirement of IPL’s senior debentures in July 2025 ($50 million, 5.5%) and August 2025 ($250 million, 3.4%), to reduce cash amounts received from its sale of accounts receivable program and commercial paper classified as long-term debt, and for general corporate purposes.
In September 2025, IPL issued $300 million of 5.6% senior debentures due 2055. The net proceeds from this issuance were used to reduce cash amounts received from its sale of accounts receivable program, reduce its outstanding commercial paper and for general corporate purposes.
In September 2025, Alliant Energy issued $725 million of junior subordinated notes due 2056. The notes will bear interest at 5.75% until April 1, 2031. The interest rate will reset every 5 years beginning April 1, 2031, to equal the then-current five-year U.S. Treasury rate plus a spread of 2.077%, provided the interest rate will not reset below 5.75%. A portion of the net proceeds from this issuance were placed in time deposits and money market fund investments pending the retirement of AEF’s $200 million of 1.40% senior notes, AEF’s $300 million variable rate term loan and Alliant Energy’s $575 million of 3.875% convertible senior notes, each of which matures in March 2026 and is expected to be retired at or prior to maturity. The remainder of the net proceeds were used to reduce outstanding commercial paper and for general corporate purposes.
Convertible Senior Notes - In May 2025, Alliant Energy issued $575 million of 3.25% convertible senior notes (the 2028 Notes), which are senior unsecured obligations, and used the net proceeds from the issuance to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. The 2028 Notes will mature on May 30, 2028 unless earlier converted or repurchased, and no sinking fund is provided for the 2028 Notes. Alliant Energy may not redeem the 2028 Notes prior to the maturity date. Holders may convert their 2028 Notes at their option at any time prior to the close of business on the business day immediately preceding March 1, 2028 only under the following circumstances:
•during any calendar quarter commencing after the calendar quarter ending on September 30, 2025 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day during such period;
•during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $1,000 principal amount of 2028 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or
•upon the occurrence of specified corporate events.
O n or after March 1, 2028 until the cl ose of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their 2028 Notes at any time, regardless of the foregoing circumstances. Upon conversion of the 2028 Notes, Alliant Energy will pay cash up to the aggregate principal amount of the 2028 Notes to be converted and pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the 2028 Notes being converted.

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The initial conversion rate is 13.1773 shares of common stock per $1,000 principal amount of 2028 Notes (equivalent to an initial conversion price of approximately $75.89 per share of Alliant Energy’s common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its 2028 Notes in connection with such a corporate event.
If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the 2028 Notes may require Alliant Energy to repurchase for cash all or any portion of its 2028 Notes at a fundamental change repurchase price equal to 100% of the principal amount of the 2028 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.
As of September 30, 2025, the conditions allowing holders of the 2028 Notes and Alliant Energy’s convertible senior notes due 2026 (the 2026 Notes) to convert their respective notes were not met, and the 2028 Notes were classified as “Long-term debt, net” and the 2026 Notes were classified as “Current maturities of long-term debt,” on Alliant Energy’s balance sheet. As of September 30, 2025, the net carrying amount was $569 million and $574 million, with unamortized debt issuance costs of $6 million and $1 million, and the estimated fair value (Level 2) was $593 million and $619 million for the 2028 Notes and 2026 Notes, respectively. As of September 30, 2025, no shares of Alliant Energy’s common stock and 27,905 shares of Alliant Energy’s common stock related to the potential conversion of the 2028 Notes and 2026 Notes, respectively, were included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the respective notes.
NOTE 8. REVENUES
Disaggregation of revenues from contracts with customers is provided for each reportable segment (IPL and WPL), as well as by customer class within electric and gas sales, as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Electric Utility: |  |  |  |  |  |  |  |  |  |  |
Retail - residential | $408 |  | $378 |  | $215 |  | $202 |  | $193 |  | $176
Retail - commercial | 282 |  | 239 |  | 192 |  | 153 |  | 90 |  | 86
Retail - industrial | 306 |  | 270 |  | 167 |  | 142 |  | 139 |  | 128
Wholesale | 51 |  | 58 |  | 11 |  | 19 |  | 40 |  | 39
Bulk power and other | 77 |  | 54 |  | 23 |  | 7 |  | 54 |  | 47
Total Electric Utility | 1,124 |  | 999 |  | 608 |  | 523 |  | 516 |  | 476
Gas Utility: |  |  |  |  |  |  |  |  |  |  |
Retail - residential | 24 |  | 24 |  | 12 |  | 13 |  | 12 |  | 11
Retail - commercial | 13 |  | 13 |  | 7 |  | 7 |  | 6 |  | 6
Retail - industrial | 1 |  | 1 |  | 1 |  | 1 |  | — |  | —
Transportation/other | 13 |  | 11 |  | 7 |  | 6 |  | 6 |  | 5
Total Gas Utility | 51 |  | 49 |  | 27 |  | 27 |  | 24 |  | 22
Other Utility: |  |  |  |  |  |  |  |  |  |  |
Steam | 9 |  | 9 |  | 9 |  | 9 |  | — |  | —
Other utility | 3 |  | 3 |  | 3 |  | 2 |  | — |  | 1
Total Other Utility | 12 |  | 12 |  | 12 |  | 11 |  | — |  | 1
Non-Utility and Other: |  |  |  |  |  |  |  |  |  |  |
Travero and other | 23 |  | 21 |  | — |  | — |  | — |  | —
Total Non-Utility and Other | 23 |  | 21 |  | — |  | — |  | — |  | —
Total revenues | $1,210 |  | $1,081 |  | $647 |  | $561 |  | $540 |  | $499

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| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Electric Utility: |  |  |  |  |  |  |  |  |  |  |
Retail - residential | $1,027 |  | $966 |  | $512 |  | $502 |  | $515 |  | $464
Retail - commercial | 705 |  | 616 |  | 462 |  | 385 |  | 243 |  | 231
Retail - industrial | 782 |  | 730 |  | 403 |  | 372 |  | 379 |  | 358
Wholesale | 148 |  | 147 |  | 39 |  | 45 |  | 109 |  | 102
Bulk power and other | 166 |  | 120 |  | 39 |  | 14 |  | 127 |  | 106
Total Electric Utility | 2,828 |  | 2,579 |  | 1,455 |  | 1,318 |  | 1,373 |  | 1,261
Gas Utility: |  |  |  |  |  |  |  |  |  |  |
Retail - residential | 211 |  | 189 |  | 107 |  | 103 |  | 104 |  | 86
Retail - commercial | 106 |  | 92 |  | 49 |  | 48 |  | 57 |  | 44
Retail - industrial | 10 |  | 8 |  | 6 |  | 5 |  | 4 |  | 3
Transportation/other | 39 |  | 33 |  | 23 |  | 19 |  | 16 |  | 14
Total Gas Utility | 366 |  | 322 |  | 185 |  | 175 |  | 181 |  | 147
Other Utility: |  |  |  |  |  |  |  |  |  |  |
Steam | 28 |  | 29 |  | 28 |  | 29 |  | — |  | —
Other utility | 9 |  | 7 |  | 8 |  | 5 |  | 1 |  | 2
Total Other Utility | 37 |  | 36 |  | 36 |  | 34 |  | 1 |  | 2
Non-Utility and Other: |  |  |  |  |  |  |  |  |  |  |
Travero and other | 67 |  | 68 |  | — |  | — |  | — |  | —
Total Non-Utility and Other | 67 |  | 68 |  | — |  | — |  | — |  | —
Total revenues | $3,298 |  | $3,005 |  | $1,676 |  | $1,527 |  | $1,555 |  | $1,410

NOTE 9. INCOME TAXES
Income Tax Rates - Overall effective income tax rates for the three and nine months ended September 30, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, investment tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Also impacting Alliant Energy’s and IPL’s effective income tax rates for the nine months ended September 30, 2024 were the pre-tax non-cash charge of $60 million for IPL’s Lansing Generating Station discussed in Note 2 and the pre-tax non-cash charge of $20 million for the AROs allocated to IPL’s steam business discussed in Note 1(d). Alliant Energy’s, IPL’s and WPL’s effective income tax rates for the three and nine months ended September 30, 2025 were also impacted by additional tax credits in 2025 from renewable generation and energy storage projects placed in service in 2024 and/or expected to be placed in service in 2025.

| Alliant Energy |  | IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Overall income tax rate | (7%) |  | (27%) |  | (19%) |  | (24%) |  | (15%) |  | (56%) |  | (36%) |  | (70%) |  | 1% |  | 3% |  | (3%) |  | 5%

Deferred Tax Assets and Liabilities -
Carryforwards - At September 30, 2025, the carryforwards and expiration dates were estimated as follows (in millions):

| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
State net operating losses | 2025-2045 |  | $249 |  | $7 |  | $1
Federal tax credits | 2034-2045 |  | 741 |  | 464 |  | 263

State Income Tax Apportionment - Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state income tax apportionment. Estimates of state income tax apportionment are supported by historical data and reasonable projections. Alliant Energy currently expects an increase in total state income tax apportionment primarily due to an increase in projected electric utility revenues driven by demand for energy from commercial and industrial customers, including demand from IPL’s and WPL’s executed electric service agreements with customers who expect to build data centers in their service territories. Alliant Energy parent company’s deferred tax assets were remeasured to reflect an increase in estimated total state income tax apportionment, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in the third quarter of 2025.

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NOTE 10. BENEFIT PLANS
NOTE 10(a) Pension and OPEB Plans -
Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.

| Defined Benefit Pension Plans |  | OPEB Plans
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
Alliant Energy | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Service cost | $1 |  | $1 |  | $3 |  | $3 |  | $— |  | $1 |  | $1 |  | $2
Interest cost | 11 |  | 12 |  | 34 |  | 34 |  | 2 |  | 2 |  | 6 |  | 6
Expected return on plan assets | (13) |  | (14) |  | (40) |  | (41) |  | — |  | (2) |  | (3) |  | (4)
Amortization of prior service credit | (1) |  | — |  | (1) |  | — |  | — |  | — |  | — |  | —
Amortization of actuarial loss | 6 |  | 6 |  | 17 |  | 18 |  | — |  | — |  | — |  | —
| $4 |  | $5 |  | $13 |  | $14 |  | $2 |  | $1 |  | $4 |  | $4

| Defined Benefit Pension Plans |  | OPEB Plans
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
IPL | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Service cost | $1 |  | $1 |  | $2 |  | $2 |  | $— |  | $— |  | $— |  | $—
Interest cost | 5 |  | 5 |  | 15 |  | 15 |  | — |  | 1 |  | 2 |  | 3
Expected return on plan assets | (7) |  | (7) |  | (19) |  | (20) |  | (1) |  | (1) |  | (3) |  | (3)
Amortization of actuarial loss | 3 |  | 2 |  | 7 |  | 7 |  | — |  | — |  | — |  | —
| $2 |  | $1 |  | $5 |  | $4 |  | ($1) |  | $— |  | ($1) |  | $—

| Defined Benefit Pension Plans |  | OPEB Plans
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
WPL | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Service cost | $— |  | $— |  | $1 |  | $1 |  | $— |  | $— |  | $— |  | $—
Interest cost | 5 |  | 5 |  | 15 |  | 15 |  | 1 |  | 1 |  | 2 |  | 3
Expected return on plan assets | (5) |  | (6) |  | (17) |  | (18) |  | (1) |  | (1) |  | (1) |  | (1)
Amortization of actuarial loss | 3 |  | 3 |  | 8 |  | 9 |  | — |  | — |  | — |  | —
| $3 |  | $2 |  | $7 |  | $7 |  | $— |  | $— |  | $1 |  | $2

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Compensation expense | $6 |  | $3 |  | $13 |  | $10 |  | $3 |  | $2 |  | $7 |  | $5 |  | $2 |  | $1 |  | $6 |  | $4
Income tax benefits | 2 |  | 1 |  | 4 |  | 3 |  | 1 |  | — |  | 2 |  | 1 |  | 1 |  | — |  | 2 |  | 1

As of September 30, 2025, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $17 million, $8 million and $8 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years.
For the nine months ended September 30, 2025, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.

|  |  | Weighted Average
| Grants |  | Grant Date Fair Value
Performance shares (total shareowner return metric) | 105,896 |  | $66.52
Performance shares (net income and environmental metrics) | 118,883 |  | 61.63
Restricted stock units | 100,245 |  | 61.66

As of September 30, 2025, 598,077 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

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NOTE 11. DERIVATIVE INSTRUMENTS
Commodity Derivatives -
Notional Amounts - As of September 30, 2025, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

| Electricity |  | FTRs |  | Natural Gas |  |  |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  |  |  |  |  | Gallons |  | Years
Alliant Energy | 1,689 |  |  | 2025-2026 |  | 17,992 |  |  | 2025-2026 |  | 136,910 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
IPL | 563 |  |  | 2025-2026 |  | 7,143 |  |  | 2025-2026 |  | 56,355 |  |  | 2025-2030 |  |  |  |  |  | — |  |  | —
WPL | 1,126 |  |  | 2025-2026 |  | 10,849 |  |  | 2025-2026 |  | 80,555 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Current derivative assets | $55 |  | $41 |  | $38 |  | $29 |  | $17 |  | $12
Non-current derivative assets | 27 |  | 34 |  | 14 |  | 19 |  | 13 |  | 15
Current derivative liabilities | 22 |  | 26 |  | 8 |  | 11 |  | 14 |  | 15
Non-current derivative liabilities | 26 |  | 32 |  | 2 |  | 2 |  | 24 |  | 30

Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets result in comparable changes to regulatory assets/liabilities on the balance sheets.
Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At September 30, 2025 and December 31, 2024, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.
Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
| Gross |  |  |  | Gross |  |  |  | Gross |  |
| (as reported) |  | Net |  | (as reported) |  | Net |  | (as reported) |  | Net
September 30, 2025 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | $82 |  | $72 |  | $52 |  | $47 |  | $30 |  | $25
Derivative liabilities | 48 |  | 38 |  | 10 |  | 5 |  | 38 |  | 33
December 31, 2024 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | 75 |  | 64 |  | 48 |  | 43 |  | 27 |  | 21
Derivative liabilities | 58 |  | 47 |  | 13 |  | 8 |  | 45 |  | 39

Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

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NOTE 12. FAIR VALUE MEASUREMENTS
Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy | September 30, 2025 |  | December 31, 2024
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $477 |  |  | $477 |  |  | $— |  |  | $— |  |  | $477 |  |  | $52 |  |  | $52 |  |  | $— |  |  | $— |  |  | $52 |
Time deposits | 250 |  |  | — |  |  | 250 |  |  | — |  |  | 250 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Commodity derivatives | 82 |  |  | — |  |  | 42 |  |  | 40 |  |  | 82 |  |  | 75 |  |  | — |  |  | 48 |  |  | 27 |  |  | 75 |
Deferred proceeds | 231 |  |  | — |  |  | — |  |  | 231 |  |  | 231 |  |  | 163 |  |  | — |  |  | — |  |  | 163 |  |  | 163 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 48 |  |  | — |  |  | 47 |  |  | 1 |  |  | 48 |  |  | 58 |  |  | — |  |  | 56 |  |  | 2 |  |  | 58 |
Long-term debt (incl. current maturities) | 11,729 |  |  | — |  |  | 11,504 |  |  | — |  |  | 11,504 |  |  | 9,848 |  |  | — |  |  | 9,577 |  |  | — |  |  | 9,577 |

IPL | September 30, 2025 |  | December 31, 2024
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $194 |  |  | $194 |  |  | $— |  |  | $— |  |  | $194 |  |  | $9 |  |  | $9 |  |  | $— |  |  | $— |  |  | $9 |
Commodity derivatives | 52 |  |  | — |  |  | 21 |  |  | 31 |  |  | 52 |  |  | 48 |  |  | — |  |  | 26 |  |  | 22 |  |  | 48 |
Deferred proceeds | 231 |  |  | — |  |  | — |  |  | 231 |  |  | 231 |  |  | 163 |  |  | — |  |  | — |  |  | 163 |  |  | 163 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 10 |  |  | — |  |  | 9 |  |  | 1 |  |  | 10 |  |  | 13 |  |  | — |  |  | 11 |  |  | 2 |  |  | 13 |
Long-term debt (incl. current maturities) | 4,679 |  |  | — |  |  | 4,465 |  |  | — |  |  | 4,465 |  |  | 4,090 |  |  | — |  |  | 3,736 |  |  | — |  |  | 3,736 |

WPL | September 30, 2025 |  | December 31, 2024
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $— |  |  | $— |  |  | $— |  |  | $— |  |  | $— |  |  | $43 |  |  | $43 |  |  | $— |  |  | $— |  |  | $43 |
Commodity derivatives | 30 |  |  | — |  |  | 21 |  |  | 9 |  |  | 30 |  |  | 27 |  |  | — |  |  | 22 |  |  | 5 |  |  | 27 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 38 |  |  | — |  |  | 38 |  |  | — |  |  | 38 |  |  | 45 |  |  | — |  |  | 45 |  |  | — |  |  | 45 |
Long-term debt | 3,372 |  |  | — |  |  | 3,287 |  |  | — |  |  | 3,287 |  |  | 3,370 |  |  | — |  |  | 3,170 |  |  | — |  |  | 3,170 |

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024
Beginning balance, July 1 | $56 |  | $51 |  | $235 |  | $171
Total n et gains (losses) i ncluded in changes in net assets (realized/unrealized) | (2) |  | 2 |  | — |  | —
Sales | (2) |  | — |  | — |  | —
Settlements (a) | (13) |  | (16) |  | (4) |  | 41
Ending balance, September 30 | $39 |  | $37 |  | $231 |  | $212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30 | ($4) |  | $2 |  | $— |  | $—

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Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Nine Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024
Beginning balance, January 1 | $25 |  | $24 |  | $163 |  | $216
Total net gains (losses) included in changes in net assets (realized/unrealized) | 5 |  | (7) |  | — |  | —
Purchases | 50 |  | 59 |  | — |  | —
Sales | (2) |  | (1) |  | — |  | —
Settlements (a) | (39) |  | (38) |  | 68 |  | (4)
Ending balance, September 30 | $39 |  | $37 |  | $231 |  | $212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30 | $4 |  | ($7) |  | $— |  | $—

IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024
Beginning balance, July 1 | $44 |  | $40 |  | $235 |  | $171
Total net losses included in changes in net assets (realized/unrealized) | (5) |  | — |  | — |  | —
Sales | (1) |  | — |  | — |  | —
Settlements (a) | (8) |  | (11) |  | (4) |  | 41
Ending balance, September 30 | $30 |  | $29 |  | $231 |  | $212
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30 | ($6) |  | $— |  | $— |  | $—

IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Nine Months Ended September 30 | 2025 |  | 2024 |  | 2025 |  | 2024
Beginning balance, January 1 | $20 |  | $19 |  | $163 |  | $216
Total net gains (losses) included in changes in net assets (realized/unrealized) | 1 |  | (7) |  | — |  | —
Purchases | 40 |  | 45 |  | — |  | —
Sales | (1) |  | (1) |  | — |  | —
Settlements (a) | (30) |  | (27) |  | 68 |  | (4)
Ending balance, September 30 | $30 |  | $29 |  | $231 |  | $212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30 | $1 |  | ($7) |  | $— |  | $—

WPL | Commodity Contract Derivative
| Assets and (Liabilities), net
Three Months Ended September 30 | 2025 |  | 2024
Beginning balance, July 1 | $12 |  | $11
Total net gains included in changes in net assets (realized/unrealized) | 3 |  | 2
Sales | (1) |  | —
Settlements | (5) |  | (5)
Ending balance, September 30 | $9 |  | $8
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 | $2 |  | $2

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WPL | Commodity Contract Derivative
| Assets and (Liabilities), net
Nine Months Ended September 30 | 2025 |  | 2024
Beginning balance, January 1 | $5 |  | $5
Total net gains included in changes in net assets (realized/unrealized) | 4 |  | —
Purchases | 10 |  | 14
Sales | (1) |  | —
Settlements | (9) |  | (11)
Ending balance, September 30 | $9 |  | $8
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 | $3 |  | $—

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Commodity Contracts - The fair value of FTRs and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
September 30, 2025 | $3 |  | $36 |  | $3 |  | $27 |  | $— |  | $9
December 31, 2024 | — |  | 25 |  | — |  | 20 |  | — |  | 5

NOTE 13. COMMITMENTS AND CONTINGENCIES
NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including improvements at the natural gas-fired Neenah Energy Facility and Sheboygan Falls Energy Facility, and IPL’s and WPL’s expansion of energy storage. At September 30, 2025, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $332 million, $136 million and $193 million, respectively.
NOTE 13(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2025, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
Natural gas | $879 |  | $489 |  | $390
Coal | 149 |  | 52 |  | 97
Other (a) | 110 |  | 52 |  | 26
| $1,138 |  | $593 |  | $513

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2025.
NOTE 13(c) Guarantees and Indemnifications -
Whiting Petroleum Corporation (Whiting Petroleum) - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum, an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, has guaranteed the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations.
Whiting Petroleum previously completed bankruptcy proceedings and business combinations, which substantially reduce the likelihood that Alliant Energy will be obligated to make any payments under these guarantees. As of September 30, 2025, the currently known partnership obligations for the abandonment obligations are estimated at $54 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy is not currently aware of, nor does it currently expect to incur in the future, any material liabilities related to these guarantees and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2025 and December 31, 2024.

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Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term purchased power agreement (PPA). Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $35 million as of September 30, 2025 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2025 and December 31, 2024.
Transfers of Renewable Tax Credits - IPL and WPL have entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash. As of September 30, 2025, IPL and WPL provided indemnifications associated with $283 million and $148 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in the event of an adverse interpretation of tax law, including whether the related tax credits meet the qualification requirements. Alliant Energy, IPL and WPL believe the likelihood of having to make any material cash payments under these indemnifications is remote.
Electric Transmission Infrastructure - IPL and WPL have entered into agreements with their respective electric transmission service providers related to the construction of infrastructure necessary for the data centers that are expected to be built in IPL’s and WPL’s service territories by certain of their customers. If these construction projects were to be terminated prior to the infrastructure being placed in service by the electric transmission service providers, then IPL or WPL must reimburse their respective provider for the related costs incurred to-date. As of September 30, 2025, IPL’s and WPL’s related guarantees were approximately $35 million and $44 million, respectively. Alliant Energy, IPL and WPL are not aware of any material liabilities related to these guarantees that it is probable that they will be obligated to pay and therefore have not recognized any material liabilities related to these guarantees as of September 30, 2025.
NOTE 13(d) Environmental Matters -
Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2025, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
Range of estimated future costs | $7 |  | - | $29 |  | $5 |  | - | $18 |  | $2 |  | - | $11
Current and non-current environmental liabilities | $12 |  | $8 |  | $4

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.
Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Cross-State Air Pollution Rule, Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the Clean Air Act.

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NOTE 14. SEGMENTS OF BUSINESS
Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
Three Months Ended September 30, 2025 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $608 |  | $516 |  | $1,124 |  | N/A |  | $1,124
Gas utility revenues | 27 |  | 24 |  | 51 |  | N/A |  | 51
Other revenues | 12 |  | — |  | 12 |  | $23 |  | 35
Total revenues | 647 |  | 540 |  | 1,187 |  | 23 |  | 1,210
Electric production fuel and purchased power expense | 106 |  | 133 |  | 239 |  | N/A |  | 239
Electric transmission service expense | 115 |  | 51 |  | 166 |  | N/A |  | 166
Cost of gas sold expense | 7 |  | 5 |  | 12 |  | N/A |  | 12
Other operation and maintenance expense | 108 |  | 84 |  | 192 |  | 12 |  | 204
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 116 |  | 92 |  | 208 |  | 3 |  | 211
Interest expense | 54 |  | 43 |  | 97 |  | 31 |  | 128
Equity income from unconsolidated investments, net | — |  | (1) |  | (1) |  | (17) |  | (18)
Income tax expense (benefit) | (21) |  | 1 |  | (20) |  | 2 |  | (18)
Other (a) | (3) |  | 9 |  | 6 |  | (1) |  | 5
Net income (loss) | 165 |  | 123 |  | 288 |  | (7) |  | 281
Total assets (as of September 30, 2025) | 12,433 |  | 10,331 |  | 22,764 |  | 1,863 |  | 24,627
Investments in equity method subsidiaries (as of September 30, 2025) | 5 |  | 19 |  | 24 |  | 644 |  | 668
Construction and acquisition expenditures | 348 |  | 163 |  | 511 |  | 72 |  | 583

| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
Three Months Ended September 30, 2024 (amounts may not foot due to rounding) |  |  |  |  | Reportable |  |  |  | Energy
IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $523 |  | $476 |  | $999 |  | N/A |  | $999
Gas utility revenues | 27 |  | 22 |  | 49 |  | N/A |  | 49
Other revenues | 11 |  | 1 |  | 12 |  | $21 |  | 33
Total revenues | 561 |  | 499 |  | 1,060 |  | 21 |  | 1,081
Electric production fuel and purchased power expense | 79 |  | 112 |  | 191 |  | N/A |  | 192
Electric transmission service expense | 115 |  | 49 |  | 164 |  | N/A |  | 165
Cost of gas sold expense | 8 |  | 5 |  | 13 |  | N/A |  | 13
Other operation and maintenance expense | 96 |  | 72 |  | 168 |  | 6 |  | 174
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 100 |  | 91 |  | 191 |  | 4 |  | 195
Interest expense | 44 |  | 42 |  | 86 |  | 28 |  | 114
Equity income from unconsolidated investments, net | — |  | (1) |  | (1) |  | (13) |  | (14)
Income tax expense (benefit) | (68) |  | 4 |  | (64) |  | 2 |  | (62)
Other (a) | (3) |  | 11 |  | 8 |  | 3 |  | 9
Net income (loss) | 190 |  | 114 |  | 304 |  | (9) |  | 295
Total assets (as of September 30, 2024) | 11,680 |  | 9,938 |  | 21,618 |  | 1,211 |  | 22,829
Investments in equity method subsidiaries (as of September 30, 2024) | 5 |  | 17 |  | 22 |  | 594 |  | 616
Construction and acquisition expenditures | 202 |  | 208 |  | 410 |  | 64 |  | 474

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| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
Nine Months Ended September 30, 2025 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,455 |  | $1,373 |  | $2,828 |  | N/A |  | $2,828
Gas utility revenues | 185 |  | 181 |  | 366 |  | N/A |  | 366
Other revenues | 36 |  | 1 |  | 37 |  | $67 |  | 104
Total revenues | 1,676 |  | 1,555 |  | 3,231 |  | 67 |  | 3,298
Electric production fuel and purchased power expense | 213 |  | 351 |  | 564 |  | N/A |  | 564
Electric transmission service expense | 322 |  | 152 |  | 474 |  | N/A |  | 474
Cost of gas sold expense | 89 |  | 91 |  | 180 |  | N/A |  | 180
Other operation and maintenance expense | 275 |  | 222 |  | 497 |  | 33 |  | 530
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 346 |  | 275 |  | 621 |  | 10 |  | 631
Interest expense | 154 |  | 129 |  | 283 |  | 89 |  | 372
Equity income from unconsolidated investments, net | — |  | (1) |  | (1) |  | (40) |  | (41)
Income tax benefit | (98) |  | (9) |  | (107) |  | (2) |  | (109)
Other (a) | 1 |  | 24 |  | 25 |  | 4 |  | 29
Net income (loss) | 374 |  | 321 |  | 695 |  | (27) |  | 668
Construction and acquisition expenditures | 976 |  | 511 |  | 1,487 |  | 161 |  | 1,648

| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
Nine Months Ended September 30, 2024 (amounts may not foot due to rounding) |  |  |  |  | Reportable |  |  |  | Energy
IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,318 |  | $1,261 |  | $2,579 |  | N/A |  | $2,579
Gas utility revenues | 175 |  | 147 |  | 322 |  | N/A |  | 322
Other revenues | 34 |  | 2 |  | 36 |  | $68 |  | 104
Total revenues | 1,527 |  | 1,410 |  | 2,937 |  | 68 |  | 3,005
Electric production fuel and purchased power expense | 195 |  | 298 |  | 493 |  | N/A |  | 493
Electric transmission service expense | 317 |  | 148 |  | 465 |  | N/A |  | 464
Cost of gas sold expense | 85 |  | 67 |  | 152 |  | N/A |  | 152
Asset valuation charge for IPL’s Lansing Generating Station | 60 |  | — |  | 60 |  | N/A |  | 60
Other operation and maintenance expense | 281 |  | 200 |  | 481 |  | 29 |  | 510
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 294 |  | 269 |  | 563 |  | 8 |  | 571
Interest expense | 128 |  | 124 |  | 252 |  | 77 |  | 329
Equity income from unconsolidated investments, net | — |  | (2) |  | (2) |  | (42) |  | (44)
Income tax expense (benefit) | (112) |  | 13 |  | (99) |  | (5) |  | (104)
Other (a) | 7 |  | 23 |  | 30 |  | 3 |  | 34
Net income (loss) | 272 |  | 270 |  | 542 |  | (2) |  | 540
Construction and acquisition expenditures | 702 |  | 578 |  | 1,280 |  | 154 |  | 1,434

(a)Other segment items for each reportable segment include allowance for funds used during construction, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

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NOTE 15. RELATED PARTIES
Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Corporate Services billings | $50 |  | $42 |  | $147 |  | $134 |  | $49 |  | $38 |  | $144 |  | $124
Sales credited | 16 |  | — |  | 18 |  | — |  | 44 |  | 29 |  | 106 |  | 66
Purchases billed | 124 |  | 130 |  | 323 |  | 332 |  | 15 |  | 18 |  | 51 |  | 41

Net intercompany payables to Corporate Services were as follows (in millions):

| IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Net payables to Corporate Services | $142 |  | $135 |  | $71 |  | $64

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
ATC billings to WPL | $38 |  | $39 |  | $114 |  | $115
WPL billings to ATC | 9 |  | 5 |  | 20 |  | 12

WPL owed ATC net amounts of $10 million as of September 30, 2025 and $10 million as of December 31, 2024.
ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
This MDA includes information relating to Alliant Energy, and IPL and WPL (collectively, the Utilities), as well as ATC Holdings, AEF and Corporate Services. Where appropriate, information relating to a specific entity has been segregated and labeled as such. The following discussion and analysis should be read in conjunction with the Financial Statements and the Notes included in this report, as well as the financial statements, notes and MDA included in the 2024 Form 10-K. Unless otherwise noted, all “per share” references in MDA refer to earnings per diluted share.
2025 HIGHLIGHTS
Key highlights since the filing of the 2024 Form 10-K include the following:
Customer Investments:
•Over the next six years, Alliant Energy currently plans to develop and/or acquire new generation investments to add flexibility with evolving load growth, including approximately 2,000 MW of natural gas resources, approximately 1,300 MW of new energy storage, approximately 1,100 MW of new renewable generation, improvements of approximately 530 MW at existing natural gas-fired EGUs, and refurbishments at approximately 450 MW of existing wind farms. Alliant Energy is currently evaluating the impact of potential additional large load growth customers and MISO’s seasonal resource adequacy requirements on its resource plans and will update these generation investment plans as needed in the future. Estimated capital expenditures for these planned projects for 2025 through 2029 are included in the “Generation” section in the construction and acquisition table in “Liquidity and Capital Resources.” Information on IPL’s and WPL’s regulatory filings and/or approvals for future generation and energy storage projects are as follows:
•In February 2025, WPL filed a certificate of authority (CA) application with the PSCW for approval to construct a 2 billion cubic feet, or 25 million gallon, liquified natural gas facility in Rock County, Wisconsin. A decision from the PSCW is currently expected in the second quarter of 2026.
•In April 2025, the PSCW issued an order authorizing WPL to construct, own and operate a 17.5 MW natural gas-fired EGU using Reciprocating Internal Combustion Engine (RICE) technology, at the site of its Riverside Energy Center.
•In April 2025, WPL filed a CA application with the PSCW for approval to construct, own and operate the Bent Tree North EGU, an approximate 153 MW wind farm. A decision from the PSCW is currently expected in the second quarter of 2026.

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•In May 2025, the PSCW issued an order authorizing WPL to refurbish the Bent Tree wind farm.
•In June 2025, the IUC issued an order authorizing IPL to construct, own and operate the Cedar River Generating Station, a 94 MW natural gas-fired EGU using RICE technology, at the site of its Prairie Creek Generating Station.
•In June 2025, the PSCW issued an order authorizing WPL to construct, own and operate an approximately 20 MW compressed carbon dioxide-based long-duration energy storage system at the site of its Columbia Energy Center.
•In July 2025, IPL filed for advance rate-making principles with the IUC for up to 1,000 MW of new wind generation in Iowa. The advance rate-making principles filing included requests for a fixed cost cap of $3,020/kilowatt, including allowance for funds used during construction and transmission upgrade costs among other costs, and a return on common equity of 11.25%. A decision from the IUC is currently expected in the first quarter of 2026.
•In July 2025, the IUC issued an order authorizing IPL to construct, own and operate up to 150 MW of energy storage at the site of its retired Lansing Generating Station.
•In July 2025, WPL completed construction of approximately 100 MW of energy storage at the site of its Grant County solar facility.
•In August 2025, the IUC issued an order authorizing IPL to construct, own and operate up to 75 MW of energy storage at the site of its Golden Plains wind farm.
•In August 2025, IPL filed a certificate of public convenience, use and necessity (GCU Certificate) application with the IUC for approval to construct, own and operate an approximate 720 MW simple-cycle natural gas-fired EGU at the site of its Marshalltown Generating Station, known as the Bobcat Energy Center. A decision from the IUC is currently expected in the first quarter of 2026.
•In September 2025, the IUC issued an order authorizing IPL to construct, own and operate up to 75 MW of energy storage at the site of its Whispering Willow - North wind farm.
•In October 2025, WPL completed construction of approximately 75 MW of energy storage at the site of its Wood County solar facility.
•In November 2025, IPL filed a GCU Certificate application with the IUC for approval to construct, own and operate a 94 MW natural gas-fired EGU using RICE technology at the site of its Burlington Generating Station. A decision from the IUC is currently expected in the first quarter of 2026.
Rate Matters:
•In September 2025, WPL filed a unanimous settlement agreement with the PSCW for the 2026/2027 forward-looking Test Period. In November 2025, the PSCW issued an oral decision approving the settlement agreement. A written order from the PSCW is currently expected by the end of 2025. The settlement agreement reflects the following:
•Annual incremental rate increases for its retail electric customers of $79 million and $73 million in 2026 (effective January 1, 2026) and 2027 (effective January 1, 2027), respectively, and an average retail electric rate base of $6,234 million and $6,549 million in 2026 and 2027, respectively.
•Annual incremental rate increases for its retail gas customers of $7 million and $5 million in 2026 (effective January 1, 2026) and 2027 (effective January 1, 2027), respectively, and an average retail gas rate base of $558 million and $593 million in 2026 and 2027, respectively.
•Return on common equity of 9.8% and common equity component of its regulatory capital structure of 54.5%.
•Key drivers include revenue requirement impacts of increasing electric and gas rate base, including wind refurbishment projects, energy storage, existing natural gas-fired EGU improvements, solar generation costs incurred that exceed the construction cost estimates previously approved by the PSCW (refer to Note 3 for further discussion), and electric and gas distribution investments.
•Extension, with certain modifications, of current earnings sharing mechanism through 2027, including deferral of a portion of earnings if the annual regulatory return on common equity exceeds 10.05% during the 2026/2027 Test Period (deferral of 50% of its excess earnings between 10.05% and 10.55%, and 100% of any excess earnings above 10.55%).
•Allowance for funds used during construction applied to 100% of construction work in progress balances related to construction activity on capital projects requiring PSCW approval and are impacted by federal law changes.
•IPL currently expects to file a subsequent proceeding with the IUC in the fourth quarter of 2025 for its October 2024 through September 2025 forward-looking Test Period retail electric and gas rate reviews, which will compare actual revenues and costs to those initially forecasted by IPL. IPL currently does not expect any rate adjustments from the subsequent proceeding.
Growing Customer Demand:
•WPL has entered into electric service agreements with two new customers, who currently expect to build data centers in WPL’s service territory. The actual timing and amount of increases in WPL’s load are subject to various factors, including interconnections, siting approvals and actual customer demand, and any executed or future agreements with customers are not expected to result in immediate increases in load. IPL’s and WPL’s currently executed electric service agreements include aggregate, peak demands of approximately 3 gigawatts. The energy resources to serve this expected load are included in the construction and acquisition table in “Liquidity and Capital Resources.”
•In May 2025 and October 2025, the IUC issued orders, with certain conditions, approving individual customer rates for data centers expected to be constructed in IPL’s service territory. In April 2025, WPL filed a request with the PSCW for approval of an individual customer rate for a data center expected to be constructed in its service territory. A decision from the PSCW is currently expected in the first quarter of 2026.

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Environmental Matters and Stewardship:
•In March 2025, the EPA announced it expects to initiate a formal reconsideration of various environmental regulations and programs, including the Cross-State Air Pollution Rule and Effluent Limitation Guidelines. In June 2025, the EPA proposed to repeal emissions standards and guidelines issued under Clean Air Act Sections 111(b) and 111(d) for electric generating units. In July 2025, the EPA proposed to repeal its 2009 finding that GHG contributes to climate change, which gave it authority to regulate GHG under the Clean Air Act. In October 2025, the EPA proposed a rule to revise certain deadlines and other provisions of the 2024 Effluent Limitation Guidelines. The EPA also expects to expedite review of state programs to delegate implementation of the Coal Combustion Residuals Rule and reconsider compliance deadlines. Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these matters, including resolution of ongoing and potential litigation.
•Alliant Energy’s current voluntary environmental stewardship goals include the following:
•By 2030, reduce GHG emissions from its utility operations by 50% from 2005 levels, reduce its electric utility water supply by 75% from 2005 levels and electrify 100% of its owned light-duty fleet vehicles.
•By 2040, eliminate all coal-fired EGUs from its generating fleet.
•By 2050, aspire to achieve net-zero GHG emissions from its utility operations.
•Alliant Energy’s aspirational GHG goal includes EPA reportable emissions based on applicable regulatory compliance requirements for carbon dioxide, methane and nitrous oxide from its owned fossil-fueled EGUs and distribution of natural gas. Alliant Energy’s voluntary environmental stewardship goals may be revised, or their achievement may be delayed, based on increasing customer energy needs, reliability and resource adequacy requirements, and tax policy changes, and the ability to achieve these goals is subject to various additional risk factors included in the 2024 Form 10-K. These goals are not meant to be considered guidance.
Legislative Matters:
•In July 2025, the One Big Beautiful Bill Act was enacted, which modifies various clean energy tax credits under the Inflation Reduction Act of 2022, including production tax credits and investment tax credits. The most significant provisions of the new legislation for Alliant Energy, IPL and WPL relate to the accelerated phase out of clean energy tax credits for eligible projects for which construction begins more than 12 months after the date of enactment or for projects placed in service after 2027, and restricted access to clean energy tax credits for projects that begin construction after 2025 and receive impermissible amounts of construction support from entities with ties to certain foreign countries, including China. Additionally, in July 2025, the Presidential Administration directed the U.S. Department of the Treasury to strictly enforce the termination of clean energy tax credits, including issuing new and revised guidance in August 2025, to ensure that requirements concerning the beginning of construction are not circumvented. Refer to “2025 Highlights” for discussion of Alliant Energy’s, IPL’s and WPL’s current plans to develop and/or acquire new clean energy resources. Alliant Energy, IPL and WPL currently expect these clean energy projects would continue to be eligible for clean energy tax credits. If these clean energy projects do not begin construction within the anticipated timeframes or fail to meet other eligibility requirements, the amount of clean energy tax credits could be significantly reduced, which could adversely impact Alliant Energy’s, IPL’s and WPL’s financial condition and results of operations.
Financings and Common Stock Dividends:
•Refer to “Results of Operations” for discussion of expected future issuances of common stock in 2026 through 2029 and common stock dividends in 2026, and expected future issuances and retirements of long-term debt by the end of 2026.
•In April 2025, WPL submitted an application to the U.S. Army Corps of Engineers for up to $45 million in loans through the Corps Water Infrastructure Financing Program. If finalized, such loans would provide low interest financing for various proposed safety projects at WPL’s Kilbourn and Prairie du Sac hydro EGUs.
RESULTS OF OPERATIONS
Financial Results Overview - The table below includes diluted EPS for Utilities and Corporate Services, ATC Holdings, and Non-utility and Parent, which are non-GAAP financial measures. Alliant Energy believes these non-GAAP financial measures are useful to investors because they facilitate an understanding of performance and trends, and provide additional information about Alliant Energy’s operations on a basis consistent with the measures that management uses to manage its operations and evaluate its performance. Alliant Energy’s net income and EPS attributable to Alliant Energy common shareowners for the three months ended September 30 were as follows (dollars in millions, except per share amounts):

| 2025 |  | 2024 |
| Income (Loss) |  | EPS |  | Income (Loss) |  | EPS |
Utilities and Corporate Services | $292 |  | $1.13 |  | $308 |  | $1.20 |
ATC Holdings | 10 |  | 0.04 |  | 9 |  | 0.04 |
Non-utility and Parent | (21) |  | (0.08) |  | (22) |  | (0.09) |
Alliant Energy Consolidated | $281 |  | $1.09 |  | $295 |  | $1.15 |

Alliant Energy’s Utilities and Corporate Services net income decreased by $16 million for the three-month period, primarily due to higher other operation and maintenance expenses, the timing of income tax expense, higher depreciation and financing expenses. These items were partially offset by higher revenue requirements from IPL’s and WPL’s capital investments.

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Alliant Energy’s Non-utility and Parent net income increased $1 million for the three-month period, primarily due to the timing of income taxes, partially offset by a state income tax apportionment charge.
Net Income Variances - The following items contributed to increased (decreased) net income for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Revenues: |  |  |  |  |  |  |  |  |  |  |
Changes in electric utility (Refer to details below) | $125 |  | $85 |  | $40 |  | $249 |  | $137 |  | $112
Changes in gas utility (Refer to details below) | 2 |  | — |  | 2 |  | 44 |  | 10 |  | 34
Changes in other utility | — |  | 1 |  | (1) |  | 1 |  | 2 |  | (1)
Changes in non-utility | 2 |  | — |  | — |  | (1) |  | — |  | —
Changes in total revenues | 129 |  | 86 |  | 41 |  | 293 |  | 149 |  | 145
Operating expenses: |  |  |  |  |  |  |  |  |  |  |
Changes in electric production fuel and purchased power (Refer to details below) | (47) |  | (27) |  | (21) |  | (71) |  | (18) |  | (53)
Changes in electric transmission service (Refer to details below) | (1) |  | — |  | (2) |  | (10) |  | (5) |  | (4)
Changes in cost of gas sold (Refer to details below) | 1 |  | 1 |  | — |  | (28) |  | (4) |  | (24)
Asset valuation charge for IPL’s Lansing Generating Station in the second quarter of 2024 (Refer to Note 2 for details) | — |  | — |  | — |  | 60 |  | 60 |  | —
Changes in other operation and maintenance (Refer to details below) | (30) |  | (12) |  | (12) |  | (20) |  | 6 |  | (22)
Changes in depreciation and amortization (Higher primarily due to solar generation placed in service in 2024 and updated electric depreciation rates for IPL effective October 1, 2024) | (16) |  | (16) |  | (1) |  | (60) |  | (52) |  | (6)
Changes in taxes other than income taxes | — |  | (1) |  | 1 |  | (1) |  | 1 |  | (1)
Changes in total operating expenses | (93) |  | (55) |  | (35) |  | (130) |  | (12) |  | (110)
Changes in operating income | 36 |  | 31 |  | 6 |  | 163 |  | 137 |  | 35
Other income and deductions: |  |  |  |  |  |  |  |  |  |  |
Changes in interest expense (Higher primarily due to financings completed in 2024 and 2025) | (14) |  | (10) |  | (1) |  | (43) |  | (26) |  | (5)
Changes in equity income from unconsolidated investments, net (Refer to Note 5 for details) | 4 |  | — |  | — |  | (3) |  | — |  | —
Changes in allowance for funds used during construction | 4 |  | 2 |  | 2 |  | 7 |  | 3 |  | 4
Changes in Other | — |  | (1) |  | (1) |  | (1) |  | 2 |  | (5)
Changes in total other income and deductions | (6) |  | (9) |  | — |  | (40) |  | (21) |  | (6)
Changes in income before income taxes | 30 |  | 22 |  | 6 |  | 123 |  | 116 |  | 29
Changes in income taxes (Refer to Note 9 for details) | (44) |  | (47) |  | 3 |  | 5 |  | (14) |  | 22
Changes in net income | ($14) |  | ($25) |  | $9 |  | $128 |  | $102 |  | $51

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Electric and Gas Revenues and Sales Summary - Electric and gas revenues (in millions), and MWh and Dth sales (in thousands), for the three and nine months ended September 30 were as follows:

Alliant Energy | Electric |  | Gas
| Revenues |  | MWhs Sold |  | Revenues |  | Dths Sold
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Three Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $996 |  | $887 |  | 6,974 |  | 6,697 |  | $38 |  | $38 |  | 3,252 |  | 3,281
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 51 |  | 58 |  | 713 |  | 782 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 64 |  | 31 |  | 1,497 |  | 1,363 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 13 |  | 23 |  | 13 |  | 14 |  | 13 |  | 11 |  | 34,593 |  | 30,239
| $1,124 |  | $999 |  | 9,197 |  | 8,856 |  | $51 |  | $49 |  | 37,845 |  | 33,520
Nine Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $2,514 |  | $2,312 |  | 19,075 |  | 18,633 |  | $327 |  | $289 |  | 33,188 |  | 29,128
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 148 |  | 147 |  | 2,055 |  | 2,115 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 133 |  | 66 |  | 4,050 |  | 4,120 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 33 |  | 54 |  | 41 |  | 43 |  | 39 |  | 33 |  | 92,758 |  | 93,248
| $2,828 |  | $2,579 |  | 25,221 |  | 24,911 |  | $366 |  | $322 |  | 125,946 |  | 122,376

IPL | Electric |  | Gas
| Revenues |  | MWhs Sold |  | Revenues |  | Dths Sold
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Three Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $574 |  | $497 |  | 3,812 |  | 3,647 |  | $20 |  | $21 |  | 1,489 |  | 1,606
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 11 |  | 19 |  | 135 |  | 212 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 17 |  | — |  | 503 |  | 248 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 6 |  | 7 |  | 7 |  | 8 |  | 7 |  | 6 |  | 10,309 |  | 10,337
| $608 |  | $523 |  | 4,457 |  | 4,115 |  | $27 |  | $27 |  | 11,798 |  | 11,943
Nine Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $1,377 |  | $1,259 |  | 10,537 |  | 10,302 |  | $162 |  | $156 |  | 15,928 |  | 14,491
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 39 |  | 45 |  | 478 |  | 568 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 19 |  | (5) |  | 1,199 |  | 777 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 20 |  | 19 |  | 23 |  | 24 |  | 23 |  | 19 |  | 32,675 |  | 31,621
| $1,455 |  | $1,318 |  | 12,237 |  | 11,671 |  | $185 |  | $175 |  | 48,603 |  | 46,112

WPL | Electric |  | Gas
| Revenues |  | MWhs Sold |  | Revenues |  | Dths Sold
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Three Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $422 |  | $390 |  | 3,162 |  | 3,050 |  | $18 |  | $17 |  | 1,763 |  | 1,675
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 40 |  | 39 |  | 578 |  | 570 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 47 |  | 31 |  | 994 |  | 1,115 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 7 |  | 16 |  | 6 |  | 6 |  | 6 |  | 5 |  | 24,284 |  | 19,902
| $516 |  | $476 |  | 4,740 |  | 4,741 |  | $24 |  | $22 |  | 26,047 |  | 21,577
Nine Months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retail | $1,137 |  | $1,053 |  | 8,538 |  | 8,331 |  | $165 |  | $133 |  | 17,260 |  | 14,637
Sales for resale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wholesale | 109 |  | 102 |  | 1,577 |  | 1,547 |  | N/A |  | N/A |  | N/A |  | N/A
Bulk power and other | 114 |  | 71 |  | 2,851 |  | 3,343 |  | N/A |  | N/A |  | N/A |  | N/A
Transportation/Other | 13 |  | 35 |  | 18 |  | 19 |  | 16 |  | 14 |  | 60,083 |  | 61,627
| $1,373 |  | $1,261 |  | 12,984 |  | 13,240 |  | $181 |  | $147 |  | 77,343 |  | 76,264

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Sales Trends and Temperatures - All iant Energy’s retail electric sa les volumes increased 4% and 2% for the three and nine months ended September 30, 2025, respectively, compared to the same periods in 2024, primarily due to changes in temperatures and higher sales to industrial customers. Alliant Energy’s retail gas sales volumes increased 14% for the nine months ended September 30, 2025, compared to the same period in 2024, primarily due to changes in temperatures.
Estimated increases (decreases) to operating income from the impacts of temperatures for the three and nine months ended September 30 were as follows (in millions):

| Electric |  | Gas
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | Change |  | 2025 |  | 2024 |  | Change |  | 2025 |  | 2024 |  | Change |  | 2025 |  | 2024 |  | Change
IPL | $11 |  | $1 |  | $10 |  | $12 |  | ($7) |  | $19 |  | $— |  | ($1) |  | $1 |  | ($4) |  | ($8) |  | $4
WPL | (1) |  | — |  | (1) |  | — |  | (11) |  | 11 |  | — |  | (1) |  | 1 |  | (1) |  | (7) |  | 6
Total Alliant Energy | $10 |  | $1 |  | $9 |  | $12 |  | ($18) |  | $30 |  | $— |  | ($2) |  | $2 |  | ($5) |  | ($15) |  | $10

Electric Sales for Resale - Bulk Power and Other - Bulk power and other volume changes were due to changes in sales in the wholesale energy markets operated by MISO. These changes are impacted by several factors, including the availability and dispatch of Alliant Energy’s EGUs and electricity demand within these wholesale energy markets. Changes in bulk power and other revenues were largely offset by changes in fuel-related costs, and therefore did not have a significant impact on operating income.
Gas Transportation/Other - Gas transportation/other sales volume changes were largely due to changes in the gas volumes supplied to Alliant Energy’s natural gas-fired EGUs caused by the availability and dispatch of such EGUs.
Electric Utility Revenue Variances - The following items contributed to increased (decreased) electric utility revenues for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Higher revenue requirements (a)(b) | $118 |  | $100 |  | $18 |  | $319 |  | $271 |  | $48
Higher sales for resale bulk power and other revenues (c) | 33 |  | 17 |  | 16 |  | 67 |  | 24 |  | 43
Estimated changes in sales volumes caused by temperatures | 9 |  | 10 |  | (1) |  | 30 |  | 19 |  | 11
Higher revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense) | 7 |  | 7 |  | — |  | 14 |  | 14 |  | —
Higher (lower) revenues primarily due to changes in retail electric fuel-related costs (Refer to Electric Production Fuel and Purchased Power Expenses Variances below) | 23 |  | 17 |  | 6 |  | 10 |  | (1) |  | 11
Changes in WPL electric fuel-related costs, net of recoveries (d) | 1 |  | — |  | 1 |  | 7 |  | — |  | 7
Lower revenues at IPL due to credits on customers’ bills related to production tax credits through its fuel-related cost recovery mechanism (offset by changes in income taxes) (a) | (27) |  | (27) |  | — |  | (116) |  | (116) |  | —
Lower revenues at IPL due to credits on customers’ bills through the tax benefit rider in 2025 (partially offset by changes in income taxes) (a) | (19) |  | (19) |  | — |  | (53) |  | (53) |  | —
Lower revenues at IPL from discontinuation of renewable energy rider in 2024 (a) | (15) |  | (15) |  | — |  | (23) |  | (23) |  | —
Other | (5) |  | (5) |  | — |  | (6) |  | 2 |  | (8)
| $125 |  | $85 |  | $40 |  | $249 |  | $137 |  | $112

(a)In September 2024, the IUC issued an order authorizing an annual base rate increase of $185 million for IPL’s retail electric customers, with customers receiving partially offsetting credits for the first 12 months through a tax benefit rider, for the October 2024 through September 2025 forward-looking Test Period. Rate changes were effective October 1, 2024, which reflect revenue requirement impacts of increasing electric rate base including investments in solar generation, updated depreciation rates, and certain incremental costs incurred resulting from the 2020 derecho windstorm. In addition, effective October 1, 2024, IPL’s renewable energy rider was discontinued, and certain production tax credits are credited to IPL’s retail electric customers through IPL’s fuel-related cost recovery mechanism. Credits on IPL’s customers’ bills have been and are expected to be offset by a reduction in income tax expense.
(b)In December 2023, the PSCW issued an order authorizing an annual base rate increase of $60 million for WPL’s retail electric customers, covering the 2025 forward-looking Test Period, which reflects revenue requirement impacts of increasing electric rate base including investments in solar generation and energy storage.

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(c)Sales for resale bulk power and other revenues increased primarily due to higher prices for electricity and capacity sold by IPL and WPL to MISO wholesale energy markets. These changes were largely offset by changes in fuel-related costs.
(d)WPL’s cost recovery mechanism for retail fuel-related expenses supports deferrals of amounts that fall outside an approved fuel monitoring range of forecasted fuel-related expenses determined by the PSCW each year. The difference between revenue collected and actual fuel-related expenses incurred within the fuel monitoring range increases or decreases Alliant Energy’s and WPL’s electric utility revenues. WPL estimates the increase (decrease) to electric utility revenues from amounts within the fuel monitoring range were approximately $1 million and $3 million for the three and nine months ended September 30, 2025, respectively, compared to $0 and ($4) million for the three and nine months ended September 30, 2024, respectively.
Gas Utility Revenue Variances - The following items contributed to increased (decreased) gas utility revenues for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Higher (lower) revenues due to changes in gas costs (Refer to Cost of Gas Sold Expense Variances below) | ($1) |  | ($1) |  | $— |  | $28 |  | $4 |  | $24
Estimated changes in sales volumes caused by temperatures | 2 |  | 1 |  | 1 |  | 10 |  | 4 |  | 6
Higher revenue requirements (a) | 1 |  | 1 |  | — |  | 6 |  | 6 |  | —
Lower revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense) | — |  | — |  | — |  | (6) |  | (6) |  | —
Other | — |  | (1) |  | 1 |  | 6 |  | 2 |  | 4
| $2 |  | $— |  | $2 |  | $44 |  | $10 |  | $34

(a)In September 2024, the IUC issued an order authorizing an annual base rate increase of $10 million for IPL’s retail gas customers, for the October 2024 through September 2025 forward-looking Test Period. Rate changes were effective October 1, 2024, which reflect revenue requirement impacts of increasing gas rate base.
Electric Production Fuel and Purchased Power Expenses Variances - The following items contributed to (increased) decreased electric production fuel and purchased power expenses for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Higher electric production fuel costs (a) | ($27) |  | ($20) |  | ($7) |  | ($55) |  | ($37) |  | ($18)
Lower (higher) purchased power expense (b) | (3) |  | 2 |  | (5) |  | (13) |  | 6 |  | (19)
Changes in regulatory recovery of retail electric fuel-related costs | (17) |  | (9) |  | (8) |  | (4) |  | 13 |  | (17)
Other | — |  | — |  | (1) |  | 1 |  | — |  | 1
| ($47) |  | ($27) |  | ($21) |  | ($71) |  | ($18) |  | ($53)

(a)Electric production fuel costs increased for the three and nine months ended September 30, 2025 compared to the same periods in 2024, primarily due to higher coal volumes due to higher dispatch of coal-fired EGUs and higher natural gas prices, partially offset by lower natural gas volumes due to lower dispatch of natural gas-fired EGUs.
(b)Purchased power expense increased for the three and nine months ended September 30, 2025 compared to the same periods in 2024, primarily due to higher prices for electricity purchased at WPL.
Electric Transmission Service Expense Variances - The following items contributed to (increased) decreased electric transmission service expense for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Changes in regulatory recovery for the difference between actual electric transmission service costs and those costs used to determine rates | $4 |  | $2 |  | $2 |  | $11 |  | $3 |  | $8
Other (primarily due to changes in transmission service costs provided by third parties) | (5) |  | (2) |  | (4) |  | (21) |  | (8) |  | (12)
| ($1) |  | $— |  | ($2) |  | ($10) |  | ($5) |  | ($4)

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Cost of Gas Sold Expense Variances - The following items contributed to (increased) decreased cost of gas sold expense for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Changes in retail gas volumes and natural gas prices | ($6) |  | $1 |  | ($7) |  | ($29) |  | ($6) |  | ($23)
Changes in the regulatory recovery of gas costs | 7 |  | — |  | 7 |  | 1 |  | 2 |  | (1)
| $1 |  | $1 |  | $— |  | ($28) |  | ($4) |  | ($24)

Other Operation and Maintenance Expenses Variances - The following items contributed to (increased) decreased other operation and maintenance expenses for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

| Three Months |  | Nine Months
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Higher generation and energy delivery expenses | ($13) |  | ($6) |  | ($7) |  | ($11) |  | $— |  | ($11)
Higher incentive compensation expense | (5) |  | (3) |  | (2) |  | (10) |  | (5) |  | (5)
Higher energy efficiency expense at IPL (mostly offset by higher revenues) | (7) |  | (7) |  | — |  | (7) |  | (7) |  | —
Development costs for new generation | (6) |  | (4) |  | (2) |  | (6) |  | (4) |  | (2)
ARO charge in the second quarter of 2024 for steam assets at IPL (Refer to Note 1(d) for details) | — |  | — |  | — |  | 20 |  | 20 |  | —
Other | 1 |  | 8 |  | (1) |  | (6) |  | 2 |  | (4)
| ($30) |  | ($12) |  | ($12) |  | ($20) |  | $6 |  | ($22)

Other Future Considerations - In addition to items discussed in this report, the following key items could impact Alliant Energy’s, IPL’s and WPL’s future financial condition or results of operations:
•Financing Plans - Alliant Energy currently expects to issue up to $2.4 billion of common stock in aggregate from 2026 through 2029 through the distribution agreement that was executed in May 2025, its Shareholder Direct Plan (up to $25 million in common stock annually) and additional future equity offerings. For the remainder of 2025, WPL currently expects to issue up to $300 million of long-term debt. In 2026, IPL and WPL currently expect to issue up to $500 million and $300 million, respectively, of long-term debt, and AEF and/or Alliant Energy at the parent company level expect to issue up to $300 million of long-term debt in aggregate. AEF and Alliant Energy at the parent company level have $500 million and $575 million, respectively, of long-term debt maturing in 2026.
•Common Stock Dividends - Alliant Energy announced a 5% increase in its targeted 2026 annual common stock dividend to $2.14 per share, which is equivalent to a quarterly rate of $0.535 per share, beginning with the February 2026 dividend payment. The timing and amount of future dividends is subject to approval of quarterly dividend declarations from Alliant Energy’s Board of Directors, and is dependent upon earnings expectations, capital requirements, and general financial business conditions, among other factors.
•Higher Earnings on Increasing Rate Base - Alliant Energy and WPL currently expect increases in electric utility and gas utility revenues in 2026 compared to 2025 due to impacts from increasing revenue requirements related to investments in the utility business (refer to “Rate Matters” for further discussion). Additionally, Alliant Energy and IPL currently expect electric utility revenues to increase in 2026 compared to 2025 due to the expiration of tax benefit rider credits in 2025. Furthermore, Alliant Energy, IPL and WPL currently expect a decrease in the effective income tax rate in 2026 compared to 2025 due to additional renewable tax credits from renewable generation and energy storage projects placed in service and/or expected to be placed in service in 2025 and 2026. A majority of the differences between actual renewable tax credits and renewable tax credits used to determine rates are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Investment tax credits resulting from IPL energy storage projects placed in service and/or expected to be placed in service in 2025 and 2026 may be utilized to offset any revenue deficiency on an annual basis up to the earnings sharing mechanism threshold included in IPL’s retail electric rate review settlement agreement.
•Sales Trends - Alliant Energy, IPL and WPL currently expect an increase in retail electric sales in 2026 compared to 2025 driven by expected load growth from new customers who currently expect to build data centers in IPL’s and WPL’s service territories. Refer to “Growing Customer Demand” for further discussion.
•Other Operation and Maintenance Expenses - Alliant Energy, IPL and WPL currently expect an increase in other operation and maintenance expenses in 2026 compared to 2025 largely due to higher generation maintenance and energy delivery expenses.
•Depreciation and Amortization Expense - Alliant Energy, IPL and WPL currently expect an increase in depreciation and amortization expense in 2026 compared to 2025 due to capital projects placed in service in 2025 and 2026.
•Interest Expense - Alliant Energy, IPL and WPL currently expect an increase in interest expense in 2026 compared to 2025 due to financings completed in 2025 and planned in 2026 as discussed above.
•Allowance for Funds Used During Construction - Alliant Energy, IPL and WPL currently expect an increase in allowance for funds used during construction in 2026 compared to 2025 largely due to changes in construction work in progress balances related to construction activity on capital projects.

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LIQUIDITY AND CAPITAL RESOURCES
The liquidity and capital resources summary included in the 2024 Form 10-K has not changed materially, except as described below.
Liquidity Position - At September 30, 2025, Alliant Energy had $503 million of cash and cash equivalents, $250 million of short-term investments, $1,108 million ($550 million at the parent company, $350 million at IPL and $208 million at WPL) of available capacity under the single revolving credit facility and $4 million of available capacity at IPL under its sales of accounts receivable program.
Capital Structure - Financial capital structures at September 30, 2025 were as follows (Long-term Debt (including current maturities) (LD); Short-term Debt (SD); Common Equity (CE)):
(a)The long-term debt component of Alliant Energy’s financial capital structure includes junior subordinated notes classified as “Long-term debt, net” on Alliant Energy’s balance sheet (refer to Note 7 for additional information). 50% of the carrying amount of junior subordinated notes is excluded from the debt component of Alliant Energy’s debt-to-capital ratio used by the majority of rating agencies. Alliant Energy’s financial capital structure adjusted for the reclassification of 50% of the carrying amount of junior subordinated notes from long-term debt to common equity at September 30, 2025 was as follows: LD: 59%, CE: 40% and SD: 1%. The non-GAAP adjusted presentation reflecting this treatment is useful and relevant to investors in understanding how management and the rating agencies evaluate Alliant Energy’s capital structure.
Cash Flows - Selected information from the cash flows statements was as follows (in millions):

| Alliant Energy |  | IPL |  | WPL
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Cash, cash equivalents and restricted cash, January 1 | $81 |  | $63 |  | $29 |  | $53 |  | $51 |  | $7
Cash flows from (used for): |  |  |  |  |  |  |  |  |  |  |
Operating activities | 900 |  | 913 |  | 289 |  | 231 |  | 573 |  | 651
Investing activities | (1,605) |  | (940) |  | (660) |  | (332) |  | (530) |  | (464)
Financing activities | 1,127 |  | 794 |  | 551 |  | 804 |  | (83) |  | (125)
Net increase (decrease) | 422 |  | 767 |  | 180 |  | 703 |  | (40) |  | 62
Cash, cash equivalents and restricted cash, September 30 | $503 |  | $830 |  | $209 |  | $756 |  | $11 |  | $69

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Operating Activities - The following items contributed to increased (decreased) operating activity cash flows for the nine months ended September 30, 2025 compared to the same period in 2024 (in millions):

| Alliant Energy |  | IPL |  | WPL
Lower collections from IPL’s retail customers due to credits on customers’ bills related to production tax credits through its fuel-related cost recovery mechanism | ($116) |  | ($116) |  | $—
Lower collections from IPL’s retail customers due to credits on customers’ bills related to the tax benefit rider | (53) |  | (53) |  | —
Changes in income taxes paid/received (a) | (50) |  | (20) |  | (43)
Changes in interest payments | (47) |  | (31) |  | (13)
Restructuring and voluntary employee separation payments in 2025 | (25) |  | (11) |  | (12)
Lower collections from IPL’s retail customers due to discontinuation of renewable energy rider in 2024 | (23) |  | (23) |  | —
Changes in gas stored underground and prepaid gas costs | (23) |  | (10) |  | (13)
Higher collections from IPL’s and WPL’s retail electric and IPL’s retail gas base rate increases | 325 |  | 277 |  | 48
Increased collections from IPL’s and WPL’s retail customers caused by temperature impacts on electric and gas sales | 40 |  | 23 |  | 17
Other (primarily due to other changes in working capital) | (41) |  | 22 |  | (62)
| ($13) |  | $58 |  | ($78)

(a)Refer to the cash flows statements for details of renewable tax credits transferred to other corporate taxpayers during the nine months ended September 30, 2025 and 2024.
Investing Activities - The following items contributed to increased (decreased) investing activity cash flows for the nine months ended September 30, 2025 compared to the same period in 2024 (in millions):

| Alliant Energy |  | IPL |  | WPL
Purchases of short-term investments in 2025 | ($250) |  | $— |  | $—
(Higher) lower utility construction and acquisition expenditures (a) | (207) |  | (274) |  | 67
Proceeds from sales of partial ownership interests in West Riverside in 2024 | (123) |  | — |  | (123)
Changes in the amount of cash receipts on sold receivables | (67) |  | (67) |  | —
Other | (18) |  | 13 |  | (10)
| ($665) |  | ($328) |  | ($66)

(a)Largely due to higher expenditures for IPL’s energy storage and gas generation, partially offset by lower expenditures for IPL’s and WPL’s solar generation and WPL’s energy storage.
Construction and Acquisition Expenditures - Construction and acquisition expenditures and financing plans are reviewed, approved and updated as part of the strategic planning process. Changes may result from a number of reasons, including changes in expected load growth, regulatory requirements, changing legislation, not obtaining favorable and acceptable regulatory approval on certain projects, changing costs of projects due to market conditions and the impact of tariffs, improvements in technology, and improvements to ensure resiliency and reliability of the electric and gas distribution systems. Alliant Energy, IPL and WPL have not yet entered into contractual commitments relating to the majority of their anticipated future construction and acquisition expenditures. As a result, they have some discretion with regard to the level and timing of these expenditures. Construction and acquisition expenditures for 2025 through 2029 are currently anticipated as follows (in millions), which are focused on adding renewable generation and energy storage projects and dispatchable gas generation projects to meet growing customer demand for electricity, including expected future data center growth from currently executed electric service agreements, and strengthening the resiliency and reliability of the electric and gas distribution systems. Alliant Energy, IPL and WPL are currently evaluating the impacts of tariffs, recently enacted legislation and additional potential large load growth customers on their resource plans, and will update their anticipated construction and acquisition expenditures as needed in the future. Cost estimates represent Alliant Energy’s, IPL’s and WPL’s portion of construction expenditures and exclude allowance for funds used during construction and capitalized interest, if applicable.

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| Alliant Energy |  | IPL |  | WPL
| 2025 | 2026 | 2027 | 2028 | 2029 |  | 2025 | 2026 | 2027 | 2028 | 2029 |  | 2025 | 2026 | 2027 | 2028 | 2029
Generation: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Renewables and energy storage projects | $940 |  | $875 |  | $1,135 |  | $1,545 |  | $820 |  |  | $615 |  | $445 |  | $530 |  | $275 |  | $655 |  |  | $310 |  | $480 |  | $605 |  | $1,270 |  | $165 |
Gas projects | 400 |  | 1,055 |  | 1,505 |  | 1,180 |  | 985 |  |  | 230 |  | 690 |  | 1,130 |  | 920 |  | 440 |  |  | 120 |  | 330 |  | 375 |  | 260 |  | 545 |
Other | 155 |  | 180 |  | 135 |  | 175 |  | 100 |  |  | 80 |  | 80 |  | 80 |  | 55 |  | 45 |  |  | 75 |  | 100 |  | 55 |  | 120 |  | 55 |
Distribution: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Electric systems | 620 |  | 550 |  | 545 |  | 570 |  | 615 |  |  | 355 |  | 275 |  | 260 |  | 265 |  | 275 |  |  | 265 |  | 275 |  | 285 |  | 305 |  | 340 |
Gas systems | 110 |  | 135 |  | 145 |  | 105 |  | 105 |  |  | 65 |  | 70 |  | 80 |  | 40 |  | 40 |  |  | 45 |  | 65 |  | 65 |  | 65 |  | 65 |
Other | 245 |  | 250 |  | 200 |  | 220 |  | 280 |  |  | 50 |  | 40 |  | 40 |  | 40 |  | 60 |  |  | 35 |  | 40 |  | 35 |  | 40 |  | 55 |
| $2,470 |  | $3,045 |  | $3,665 |  | $3,795 |  | $2,905 |  |  | $1,395 |  | $1,600 |  | $2,120 |  | $1,595 |  | $1,515 |  |  | $850 |  | $1,290 |  | $1,420 |  | $2,060 |  | $1,225 |

Financing Activities - The following items contributed to increased (decreased) financing activity cash flows for the nine months ended September 30, 2025 compared to the same period in 2024 (in millions):

| Alliant Energy |  | IPL |  | WPL
Higher (lower) net proceeds from issuance of long-term debt | $561 |  | $245 |  | ($297)
(Higher) lower payments to retire long-term debt | 5 |  | (300) |  | —
Higher (lower) capital contributions from IPL’s and WPL’s parent company, Alliant Energy | — |  | (40) |  | 25
Net changes in the amount of commercial paper outstanding | (221) |  | (50) |  | 327
Higher common stock dividends | (22) |  | (119) |  | (16)
Other | 10 |  | 11 |  | 3
| $333 |  | ($253) |  | $42

FERC Financing Authorization - In August 2025, IPL received authorization from FERC to increase the long-term debt securities issuances in 2024 and 2025 to $1,950 million. The remaining capacity as of September 30, 2025 is $400 million.
Common Stock Issuances and Common Stock Dividends - Refer to Note 6 for discussion of common stock issuances by Alliant Energy in 2025 and Alliant Energy’s at-the-market offering program. Refer to “Results of Operations” for discussion of expected future issuances of common stock from 2026 through 2029 and common stock dividends in 2026.
Long-term Debt - Refer to Note 7(b) for discussion of AEF’s term loan credit agreements and various issuances and/or retirements of long-term debt by Alliant Energy and IPL in 2025. Refer to “Results of Operation s” for discussion of expected future issuances and retirements of long-term debt by the end of 2026.
Impact of Credit Ratings on Liquidity and Collateral Obligations -
Ratings Triggers - In March 2025, Standard & Poor’s Ratings Services changed certain Alliant Energy, IPL and WPL credit ratings and outlooks, which are not expected to have a material impact on Alliant Energy’s, IPL’s and WPL’s liquidity or collateral obligations, and the current credit ratings and outlooks are as follows:

|  | Standard & Poor’s Ratings Services |  |
Alliant Energy: | Corporate/issuer | BBB+ |  |
| Commercial paper | A-2 |  |
| Senior unsecured long-term debt | BBB |  |
| Outlook | Stable |  |
IPL: | Corporate/issuer | BBB+ |  |
| Commercial paper | A-2 |  |
| Senior unsecured long-term debt | BBB+ |  |
| Outlook | Stable |  |
WPL: | Corporate/issuer | A- |  |
| Commercial paper | A-2 |  |
| Senior unsecured long-term debt | A- |  |
| Outlook | Stable |  |

Off-Balance Sheet Arrangements and Certain Financial Commitments - A summary of Alliant Energy’s and IPL’s off-balance sheet arrangements and Alliant Energy’s, IPL’s and WPL’s contractual obligations is included in the 2024 Form 10-K and has not changed materially from the items reported in the 2024 Form 10-K, except for the items described in Notes 4, 7 and 1 3.

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OTHER MATTERS
Critical Accounting Estimates - The summary of critical accounting estimates included in the 2024 Form 10-K has not changed materially, except as described below.
Long-Lived Assets -
Regulated Operations -
Generating Units Subject to Early Retirement - WPL currently plans to continue coal operations at Columbia Units 1 and 2 at least through 2029 as well as evaluate the potential conversion of Columbia Unit 1 and/or Unit 2 to natural gas. WPL previously planned to cease coal operations at Columbia Units 1 and 2 by the end of 2029. As a result, Alliant Energy and WPL concluded that Columbia Units 1 and 2 no longer meet the criteria to be considered probable of abandonment as of September 30, 2025. Refer to Note 3 for further discussion of Columbia Units 1 and 2.
Solar Generation Projects Recently Completed - Construction costs associated with WPL’s approximately 1,100 MW of new solar generation exceeded the construction cost estimates previously approved by the PSCW by approximately $205 million. In September 2025, WPL filed a settlement agreement with the PSCW for the 2026/2027 forward-looking Test Period. In November 2025, the PSCW issued an oral decision approving the settlement agreement, which includes a full return of and on these solar generation construction costs from WPL’s retail electric customers. As a result, Alliant Energy and WPL concluded that there was not a probable disallowance of the higher rate base amounts as of September 30, 2025. Refer to Note 3 for further discussion.
Retroactive Tariffs on Solar Cells and Modules - In August 2023, the U.S. Department of Commerce (DOC) issued a final ruling that found solar cells and modules produced in certain Southeast Asian countries, including Cambodia, Malaysia, Thailand and Vietnam, using parts and components produced in China, were circumventing pre-existing antidumping and countervailing duties on China. Consistent with a June 2022 Presidential Proclamation, the DOC issued rules granting duty-free treatment of solar cells and modules imported from these four countries as of June 2022 until June 2024. In August 2025, the U.S. Court of International Trade (CIT) ruled that this two-year duty suspension, as issued, was impermissible. In September 2025, this ruling from the CIT was appealed to the Federal Circuit. The CIT's order has been stayed pending appeal. Alliant Energy, IPL and WPL continue to assess the potential impact of these tariffs on previously completed solar generation projects and are currently unable to predict with certainty the future outcome or impact of these matters, including resolution of ongoing litigation.
ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK
Quantitative and Qualitative Disclosures About Market Risk are reported in the 2024 Form 10-K and have not changed materially.
ITEM 4. CONTROLS AND PROCEDURES
Alliant Energy’s, IPL’s and WPL’s management evaluated, with the participation of each of Alliant Energy’s, IPL’s and WPL’s Chief Executive Officer, Chief Financial Officer and Disclosure Committee, the effectiveness of the design and operation of Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures (as defined in Rule 13a-15(e) of the Securities Exchange Act of 1934, as amended) as of September 30, 2025 pursuant to the requirements of the Securities Exchange Act of 1934, as amended. Based on their evaluation, the Chief Executive Officer and the Chief Financial Officer concluded that Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures were effective as of the quarter ended September 30, 2025.
There was no change in Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting that occurred during the quarter ended September 30, 2025 that has materially affected, or is reasonably likely to materially affect, Alliant Energy’s, IPL’s or WPL’s internal control over financial reporting.
PART II. OTHER INFORMATION
ITEM 1. LEGAL PROCEEDINGS
None. SEC regulations require Alliant Energy, IPL and WPL to disclose information about certain proceedings arising under federal, state or local environmental provisions when a governmental authority is a party to the proceedings and such proceedings involve potential monetary sanctions that Alliant Energy, IPL and WPL reasonably believe will exceed a specified threshold. Pursuant to the SEC regulations, Alliant Energy, IPL and WPL use a threshold of $1 million for purposes of determining whether disclosure of any such proceedings is required. Applying this threshold, there are no environmental matters to disclose for this period.
ITEM 1A. RISK FACTORS
The risk factors described in Item 1A in the 2024 Form 10-K have not changed materially.

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ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS
A summary of Alliant Energy common stock repurchases for the quarter ended September 30, 2025 was as follows:

|  | Total Number |  | Average Price |  | Total Number of Shares |  | Maximum Number (or Approximate
|  | of Shares |  | Paid Per |  | Purchased as Part of |  | Dollar Value) of Shares That May
Period |  | Purchased (a) |  | Share |  | Publicly Announced Plan |  | Yet Be Purchased Under the Plan (a)
July 1 through July 31 |  | 5,948 |  | $62.08 |  | — |  | N/A
August 1 through August 31 |  | 2,812 |  | 64.62 |  | — |  | N/A
September 1 through September 30 |  | 6 |  | 65.46 |  | — |  | N/A
|  | 8,766 |  | 62.90 |  | — |  |

(a)All shares were purchased on the open market and held in a rabbi trust under the Alliant Energy Deferred Compensation Plan. There is no limit on the number of shares of Alliant Energy common stock that may be held under the Deferred Compensation Plan, which currently does not have an expiration date.
ITEM 5. OTHER INFORMATION
(c)During the quarter ended September 30, 2025, no director or officer of Alliant Energy, IPL or WPL adopted or terminated a Rule 10b5-1 trading arrangement or non-Rule 10b5-1 trading arrangement, as each term is defined in Item 408(a) of Regulation S-K.
ITEM 6. EXHIBITS
The following Exhibits are filed herewith or incorporated herein by reference.

Exhibit Number | Description
4.1 | Officer’s Certificate, dated as of September 11, 2025, creating IPL’s 5.600% Senior Debentures due October 1, 2055 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 11, 2025 (File No. 1-4117))
4.2 | Indenture, dated as of September 26, 2025, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed September 26, 2025 (File No. 1-9894))
4.3 | First Supplemental Indenture, dated as of September 26, 2025, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee, relating to the 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 (incorporated by reference to Exhibit 4.2 to Alliant Energy’s Form 8-K, filed September 26, 2025 (File No. 1-9894))
31.1 | Certification of the Chief Executive Officer for Alliant Energy
31.2 | Certification of the Chief Financial Officer for Alliant Energy
31.3 | Certification of the Chief Executive Officer for IPL
31.4 | Certification of the Chief Financial Officer for IPL
31.5 | Certification of the Chief Executive Officer for WPL
31.6 | Certification of the Chief Financial Officer for WPL
32.1 | Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for Alliant Energy
32.2 | Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for IPL
32.3 | Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for WPL
101.INS | Inline XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document
101.SCH | Inline XBRL Taxonomy Extension Schema Document
101.CAL | Inline XBRL Taxonomy Extension Calculation Linkbase Document
101.LAB | Inline XBRL Taxonomy Extension Label Linkbase Document
101.PRE | Inline XBRL Taxonomy Extension Presentation Linkbase Document
101.DEF | Inline XBRL Taxonomy Extension Definition Linkbase Document
104 | Cover Page Interactive Data File (embedded within the Inline XBRL document)

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SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company have each duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized on t he 7th day of November 2025.

ALLIANT ENERGY CORPORATION |
Registrant |
By: /s/ Dylan M. Syse | Chief Accounting Officer and Controller
Dylan M. Syse | (Principal Accounting Officer and Authorized Signatory)

INTERSTATE POWER AND LIGHT COMPANY |
Registrant |
By: /s/ Dylan M. Syse | Chief Accounting Officer and Controller
Dylan M. Syse | (Principal Accounting Officer and Authorized Signatory)

WISCONSIN POWER AND LIGHT COMPANY |
Registrant |
By: /s/ Dylan M. Syse | Chief Accounting Officer and Controller
Dylan M. Syse | (Principal Accounting Officer and Authorized Signatory)

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