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Regulatory Matters | 3 Months Ended
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Mar. 31, 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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $939 |  | $934 |  | $839 |  | $831 |  | $100 |  | $103
Pension and OPEB costs | 340 |  | 347 |  | 168 |  | 171 |  | 172 |  | 176
Assets retired early | 267 |  | 273 |  | 253 |  | 259 |  | 14 |  | 14
Asset retirement obligations (AROs) | 200 |  | 194 |  | 165 |  | 160 |  | 35 |  | 34
Commodity cost recovery | 100 |  | 120 |  | 5 |  | 12 |  | 95 |  | 108
Derivatives | 97 |  | 102 |  | 33 |  | 34 |  | 64 |  | 68
WPL’s Western Wisconsin gas distribution expansion investments | 44 |  | 44 |  | — |  | — |  | 44 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 36 |  | 42 |  | 36 |  | 42 |  | — |  | —
Other | 197 |  | 205 |  | 68 |  | 68 |  | 129 |  | 137
| $2,220 |  | $2,261 |  | $1,567 |  | $1,577 |  | $653 |  | $684
Derivatives - Refer to Note 10 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $563 |  | $566 |  | $297 |  | $299 |  | $266 |  | $267
Cost of removal obligations | 380 |  | 366 |  | 241 |  | 242 |  | 139 |  | 124
Derivatives | 49 |  | 65 |  | 28 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 61 |  | 48 |  | 25 |  | 13 |  | 36 |  | 35
Other | 83 |  | 85 |  | 57 |  | 56 |  | 26 |  | 29
| $1,136 |  | $1,130 |  | $648 |  | $644 |  | $488 |  | $486
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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $939 |  | $934 |  | $839 |  | $831 |  | $100 |  | $103
Pension and OPEB costs | 340 |  | 347 |  | 168 |  | 171 |  | 172 |  | 176
Assets retired early | 267 |  | 273 |  | 253 |  | 259 |  | 14 |  | 14
Asset retirement obligations (AROs) | 200 |  | 194 |  | 165 |  | 160 |  | 35 |  | 34
Commodity cost recovery | 100 |  | 120 |  | 5 |  | 12 |  | 95 |  | 108
Derivatives | 97 |  | 102 |  | 33 |  | 34 |  | 64 |  | 68
WPL’s Western Wisconsin gas distribution expansion investments | 44 |  | 44 |  | — |  | — |  | 44 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 36 |  | 42 |  | 36 |  | 42 |  | — |  | —
Other | 197 |  | 205 |  | 68 |  | 68 |  | 129 |  | 137
| $2,220 |  | $2,261 |  | $1,567 |  | $1,577 |  | $653 |  | $684
Derivatives - Refer to Note 10 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $563 |  | $566 |  | $297 |  | $299 |  | $266 |  | $267
Cost of removal obligations | 380 |  | 366 |  | 241 |  | 242 |  | 139 |  | 124
Derivatives | 49 |  | 65 |  | 28 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 61 |  | 48 |  | 25 |  | 13 |  | 36 |  | 35
Other | 83 |  | 85 |  | 57 |  | 56 |  | 26 |  | 29
| $1,136 |  | $1,130 |  | $648 |  | $644 |  | $488 |  | $486
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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $939 |  | $934 |  | $839 |  | $831 |  | $100 |  | $103
Pension and OPEB costs | 340 |  | 347 |  | 168 |  | 171 |  | 172 |  | 176
Assets retired early | 267 |  | 273 |  | 253 |  | 259 |  | 14 |  | 14
Asset retirement obligations (AROs) | 200 |  | 194 |  | 165 |  | 160 |  | 35 |  | 34
Commodity cost recovery | 100 |  | 120 |  | 5 |  | 12 |  | 95 |  | 108
Derivatives | 97 |  | 102 |  | 33 |  | 34 |  | 64 |  | 68
WPL’s Western Wisconsin gas distribution expansion investments | 44 |  | 44 |  | — |  | — |  | 44 |  | 44
IPL’s Duane Arnold Energy Center PPA amendment | 36 |  | 42 |  | 36 |  | 42 |  | — |  | —
Other | 197 |  | 205 |  | 68 |  | 68 |  | 129 |  | 137
| $2,220 |  | $2,261 |  | $1,567 |  | $1,577 |  | $653 |  | $684
Derivatives - Refer to Note 10 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 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
| March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023 |  | March 31, 2024 |  | December 31, 2023
Tax-related | $563 |  | $566 |  | $297 |  | $299 |  | $266 |  | $267
Cost of removal obligations | 380 |  | 366 |  | 241 |  | 242 |  | 139 |  | 124
Derivatives | 49 |  | 65 |  | 28 |  | 34 |  | 21 |  | 31
Commodity cost recovery | 61 |  | 48 |  | 25 |  | 13 |  | 36 |  | 35
Other | 83 |  | 85 |  | 57 |  | 56 |  | 26 |  | 29
| $1,136 |  | $1,130 |  | $648 |  | $644 |  | $488 |  | $486

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