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Common Equity

9 Months Ended

Sep. 30, 2025

Common Equity [Line Items]

Common Equity

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.

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

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

IPL [Member]

Common Equity [Line Items]

Common Equity

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.

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

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

WPL [Member]

Common Equity [Line Items]

Common Equity

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.

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

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

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