Summary Of Significant Accounting Policies	9 Months Ended
Sep. 30, 2025
Summary Of Significant Accounting Policies	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.
IPL [Member]
Summary Of Significant Accounting Policies	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.
WPL [Member]
Summary Of Significant Accounting Policies	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.

Summary Of Significant Accounting Policies

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.

Summary Of Significant Accounting Policies

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.

Summary Of Significant Accounting Policies

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.