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Regulatory Matters | 9 Months Ended
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Sep. 30, 2024
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $1,000 |  | $934 |  | $885 |  | $831 |  | $115 |  | $103
AROs | 418 |  | 194 |  | 223 |  | 160 |  | 195 |  | 34
Pension and OPEB costs | 329 |  | 347 |  | 163 |  | 171 |  | 166 |  | 176
Assets retired early | 181 |  | 273 |  | 169 |  | 259 |  | 12 |  | 14
Derivatives | 80 |  | 102 |  | 24 |  | 34 |  | 56 |  | 68
Commodity cost recovery | 76 |  | 120 |  | 8 |  | 12 |  | 68 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 42 |  | 44 |  | — |  | — |  | 42 |  | 44
IPL’s Duane Arnold Energy Center purchased power agreement amendment | 24 |  | 42 |  | 24 |  | 42 |  | — |  | —
Other | 200 |  | 205 |  | 72 |  | 68 |  | 128 |  | 137
| $2,350 |  | $2,261 |  | $1,568 |  | $1,577 |  | $782 |  | $684
AROs - Refer to Note 11 for discussion of the recognition of additional ARO regulatory assets in the second quarter of 2024, substantially resulting from the enactment of the revised CCR Rule. Assets retired early - In May 2023, IPL retired the Lansing Generating Station. IPL was previously allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. In September 2024, the IUC approved the June 2024 partial non-unanimous settlement agreement between IPL and certain stakeholders for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period. The agreement includes a return of the remaining net book value of Lansing, but does 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 is 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2024, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $589 |  | $566 |  | $286 |  | $299 |  | $303 |  | $267
Cost of removal obligations | 359 |  | 366 |  | 215 |  | 242 |  | 144 |  | 124
Derivatives | 47 |  | 65 |  | 26 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 45 |  | 48 |  | 8 |  | 13 |  | 37 |  | 35
Other | 32 |  | 85 |  | 18 |  | 56 |  | 14 |  | 29
| $1,072 |  | $1,130 |  | $553 |  | $644 |  | $519 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the nine months ended September 30, 2024 was primarily due to tax benefits resulting from WPL electing investment tax credit treatment for its Cassville solar facility in the second quarter of 2024. A majority of these benefits will be addressed in a future regulatory proceeding, with a portion of the benefits passed on to WPL’s electric customers in 2024 and 2025. Rate Reviews - IPL’s Retail Electric and Gas Rate Reviews (October 2024 through September 2025 Forward-looking Test Period) - In September 2024, the IUC issued an order authorizing annual base rate increases 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, and $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, and are currently subject to procedural reviews by the IUC. The IUC’s order also reflects the following: •Electric earnings sharing mechanism beginning in calendar year 2025, where IPL would apply excess earnings to the remaining net book value of IPL’s highest earning asset with advance ratemaking principles (currently the Emery Generation Station) based on its authorized return on common equity; •Investment tax credits resulting from renewable generation and battery storage projects may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold; any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any revenue deficiency in future years; and •Discontinuation of the renewable energy rider.
IPL [Member] |
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $1,000 |  | $934 |  | $885 |  | $831 |  | $115 |  | $103
AROs | 418 |  | 194 |  | 223 |  | 160 |  | 195 |  | 34
Pension and OPEB costs | 329 |  | 347 |  | 163 |  | 171 |  | 166 |  | 176
Assets retired early | 181 |  | 273 |  | 169 |  | 259 |  | 12 |  | 14
Derivatives | 80 |  | 102 |  | 24 |  | 34 |  | 56 |  | 68
Commodity cost recovery | 76 |  | 120 |  | 8 |  | 12 |  | 68 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 42 |  | 44 |  | — |  | — |  | 42 |  | 44
IPL’s Duane Arnold Energy Center purchased power agreement amendment | 24 |  | 42 |  | 24 |  | 42 |  | — |  | —
Other | 200 |  | 205 |  | 72 |  | 68 |  | 128 |  | 137
| $2,350 |  | $2,261 |  | $1,568 |  | $1,577 |  | $782 |  | $684
AROs - Refer to Note 11 for discussion of the recognition of additional ARO regulatory assets in the second quarter of 2024, substantially resulting from the enactment of the revised CCR Rule. Assets retired early - In May 2023, IPL retired the Lansing Generating Station. IPL was previously allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. In September 2024, the IUC approved the June 2024 partial non-unanimous settlement agreement between IPL and certain stakeholders for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period. The agreement includes a return of the remaining net book value of Lansing, but does 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 is 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2024, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $589 |  | $566 |  | $286 |  | $299 |  | $303 |  | $267
Cost of removal obligations | 359 |  | 366 |  | 215 |  | 242 |  | 144 |  | 124
Derivatives | 47 |  | 65 |  | 26 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 45 |  | 48 |  | 8 |  | 13 |  | 37 |  | 35
Other | 32 |  | 85 |  | 18 |  | 56 |  | 14 |  | 29
| $1,072 |  | $1,130 |  | $553 |  | $644 |  | $519 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the nine months ended September 30, 2024 was primarily due to tax benefits resulting from WPL electing investment tax credit treatment for its Cassville solar facility in the second quarter of 2024. A majority of these benefits will be addressed in a future regulatory proceeding, with a portion of the benefits passed on to WPL’s electric customers in 2024 and 2025. Rate Reviews - IPL’s Retail Electric and Gas Rate Reviews (October 2024 through September 2025 Forward-looking Test Period) - In September 2024, the IUC issued an order authorizing annual base rate increases 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, and $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, and are currently subject to procedural reviews by the IUC. The IUC’s order also reflects the following: •Electric earnings sharing mechanism beginning in calendar year 2025, where IPL would apply excess earnings to the remaining net book value of IPL’s highest earning asset with advance ratemaking principles (currently the Emery Generation Station) based on its authorized return on common equity; •Investment tax credits resulting from renewable generation and battery storage projects may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold; any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any revenue deficiency in future years; and •Discontinuation of the renewable energy rider.
WPL [Member] |
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $1,000 |  | $934 |  | $885 |  | $831 |  | $115 |  | $103
AROs | 418 |  | 194 |  | 223 |  | 160 |  | 195 |  | 34
Pension and OPEB costs | 329 |  | 347 |  | 163 |  | 171 |  | 166 |  | 176
Assets retired early | 181 |  | 273 |  | 169 |  | 259 |  | 12 |  | 14
Derivatives | 80 |  | 102 |  | 24 |  | 34 |  | 56 |  | 68
Commodity cost recovery | 76 |  | 120 |  | 8 |  | 12 |  | 68 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 42 |  | 44 |  | — |  | — |  | 42 |  | 44
IPL’s Duane Arnold Energy Center purchased power agreement amendment | 24 |  | 42 |  | 24 |  | 42 |  | — |  | —
Other | 200 |  | 205 |  | 72 |  | 68 |  | 128 |  | 137
| $2,350 |  | $2,261 |  | $1,568 |  | $1,577 |  | $782 |  | $684
AROs - Refer to Note 11 for discussion of the recognition of additional ARO regulatory assets in the second quarter of 2024, substantially resulting from the enactment of the revised CCR Rule. Assets retired early - In May 2023, IPL retired the Lansing Generating Station. IPL was previously allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. In September 2024, the IUC approved the June 2024 partial non-unanimous settlement agreement between IPL and certain stakeholders for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period. The agreement includes a return of the remaining net book value of Lansing, but does 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 is 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2024, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023 |  | September 30, 2024 |  | December 31, 2023
Tax-related | $589 |  | $566 |  | $286 |  | $299 |  | $303 |  | $267
Cost of removal obligations | 359 |  | 366 |  | 215 |  | 242 |  | 144 |  | 124
Derivatives | 47 |  | 65 |  | 26 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 45 |  | 48 |  | 8 |  | 13 |  | 37 |  | 35
Other | 32 |  | 85 |  | 18 |  | 56 |  | 14 |  | 29
| $1,072 |  | $1,130 |  | $553 |  | $644 |  | $519 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the nine months ended September 30, 2024 was primarily due to tax benefits resulting from WPL electing investment tax credit treatment for its Cassville solar facility in the second quarter of 2024. A majority of these benefits will be addressed in a future regulatory proceeding, with a portion of the benefits passed on to WPL’s electric customers in 2024 and 2025. Rate Reviews - IPL’s Retail Electric and Gas Rate Reviews (October 2024 through September 2025 Forward-looking Test Period) - In September 2024, the IUC issued an order authorizing annual base rate increases 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, and $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, and are currently subject to procedural reviews by the IUC. The IUC’s order also reflects the following: •Electric earnings sharing mechanism beginning in calendar year 2025, where IPL would apply excess earnings to the remaining net book value of IPL’s highest earning asset with advance ratemaking principles (currently the Emery Generation Station) based on its authorized return on common equity; •Investment tax credits resulting from renewable generation and battery storage projects may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold; any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any revenue deficiency in future years; and •Discontinuation of the renewable energy rider.

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