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Regulatory Matters | 6 Months Ended
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Jun. 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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $958 |  | $934 |  | $848 |  | $831 |  | $110 |  | $103
AROs | 408 |  | 194 |  | 218 |  | 160 |  | 190 |  | 34
Pension and OPEB costs | 334 |  | 347 |  | 165 |  | 171 |  | 169 |  | 176
Assets retired early | 197 |  | 273 |  | 184 |  | 259 |  | 13 |  | 14
Derivatives | 95 |  | 102 |  | 33 |  | 34 |  | 62 |  | 68
Commodity cost recovery | 89 |  | 120 |  | 2 |  | 12 |  | 87 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 43 |  | 44 |  | — |  | — |  | 43 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 30 |  | 42 |  | 30 |  | 42 |  | — |  | —
Other | 191 |  | 205 |  | 68 |  | 68 |  | 123 |  | 137
| $2,345 |  | $2,261 |  | $1,548 |  | $1,577 |  | $797 |  | $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 is currently allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period filed with the IUC in October 2023 included a request for continued recovery of and a return on the remaining net book value of Lansing through 2037. In June 2024, IPL reached a partial non-unanimous settlement agreement with certain stakeholders, which is subject to IUC approval. 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. As a result, the return on the remaining net book value is no longer probable of recovery from IPL’s retail electric customers, and in the second quarter of 2024, 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. A decision from the IUC on the settlement agreement is currently expected in the third quarter of 2024, with final rates expected to be effective October 1, 2024. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $601 |  | $566 |  | $296 |  | $299 |  | $305 |  | $267
Cost of removal obligations | 374 |  | 366 |  | 232 |  | 242 |  | 142 |  | 124
Derivatives | 50 |  | 65 |  | 30 |  | 34 |  | 20 |  | 31
Commodity cost recovery | 51 |  | 48 |  | 16 |  | 13 |  | 35 |  | 35
Other | 60 |  | 85 |  | 44 |  | 56 |  | 16 |  | 29
| $1,136 |  | $1,130 |  | $618 |  | $644 |  | $518 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the six months ended June 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.
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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $958 |  | $934 |  | $848 |  | $831 |  | $110 |  | $103
AROs | 408 |  | 194 |  | 218 |  | 160 |  | 190 |  | 34
Pension and OPEB costs | 334 |  | 347 |  | 165 |  | 171 |  | 169 |  | 176
Assets retired early | 197 |  | 273 |  | 184 |  | 259 |  | 13 |  | 14
Derivatives | 95 |  | 102 |  | 33 |  | 34 |  | 62 |  | 68
Commodity cost recovery | 89 |  | 120 |  | 2 |  | 12 |  | 87 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 43 |  | 44 |  | — |  | — |  | 43 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 30 |  | 42 |  | 30 |  | 42 |  | — |  | —
Other | 191 |  | 205 |  | 68 |  | 68 |  | 123 |  | 137
| $2,345 |  | $2,261 |  | $1,548 |  | $1,577 |  | $797 |  | $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 is currently allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period filed with the IUC in October 2023 included a request for continued recovery of and a return on the remaining net book value of Lansing through 2037. In June 2024, IPL reached a partial non-unanimous settlement agreement with certain stakeholders, which is subject to IUC approval. 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. As a result, the return on the remaining net book value is no longer probable of recovery from IPL’s retail electric customers, and in the second quarter of 2024, 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. A decision from the IUC on the settlement agreement is currently expected in the third quarter of 2024, with final rates expected to be effective October 1, 2024. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $601 |  | $566 |  | $296 |  | $299 |  | $305 |  | $267
Cost of removal obligations | 374 |  | 366 |  | 232 |  | 242 |  | 142 |  | 124
Derivatives | 50 |  | 65 |  | 30 |  | 34 |  | 20 |  | 31
Commodity cost recovery | 51 |  | 48 |  | 16 |  | 13 |  | 35 |  | 35
Other | 60 |  | 85 |  | 44 |  | 56 |  | 16 |  | 29
| $1,136 |  | $1,130 |  | $618 |  | $644 |  | $518 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the six months ended June 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.
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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $958 |  | $934 |  | $848 |  | $831 |  | $110 |  | $103
AROs | 408 |  | 194 |  | 218 |  | 160 |  | 190 |  | 34
Pension and OPEB costs | 334 |  | 347 |  | 165 |  | 171 |  | 169 |  | 176
Assets retired early | 197 |  | 273 |  | 184 |  | 259 |  | 13 |  | 14
Derivatives | 95 |  | 102 |  | 33 |  | 34 |  | 62 |  | 68
Commodity cost recovery | 89 |  | 120 |  | 2 |  | 12 |  | 87 |  | 108
WPL’s Western Wisconsin gas distribution expansion investments | 43 |  | 44 |  | — |  | — |  | 43 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 30 |  | 42 |  | 30 |  | 42 |  | — |  | —
Other | 191 |  | 205 |  | 68 |  | 68 |  | 123 |  | 137
| $2,345 |  | $2,261 |  | $1,548 |  | $1,577 |  | $797 |  | $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 is currently allowed a full recovery of and a full return on this EGU from both its retail and wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period filed with the IUC in October 2023 included a request for continued recovery of and a return on the remaining net book value of Lansing through 2037. In June 2024, IPL reached a partial non-unanimous settlement agreement with certain stakeholders, which is subject to IUC approval. 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. As a result, the return on the remaining net book value is no longer probable of recovery from IPL’s retail electric customers, and in the second quarter of 2024, 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, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. A decision from the IUC on the settlement agreement is currently expected in the third quarter of 2024, with final rates expected to be effective October 1, 2024. Derivatives - Refer to Note 1 2 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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
| June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023 |  | June 30, 2024 |  | December 31, 2023
Tax-related | $601 |  | $566 |  | $296 |  | $299 |  | $305 |  | $267
Cost of removal obligations | 374 |  | 366 |  | 232 |  | 242 |  | 142 |  | 124
Derivatives | 50 |  | 65 |  | 30 |  | 34 |  | 20 |  | 31
Commodity cost recovery | 51 |  | 48 |  | 16 |  | 13 |  | 35 |  | 35
Other | 60 |  | 85 |  | 44 |  | 56 |  | 16 |  | 29
| $1,136 |  | $1,130 |  | $618 |  | $644 |  | $518 |  | $486
Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities during the six months ended June 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.

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