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Regulatory Matters | 9 Months Ended
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Sep. 30, 2023
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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $919 |  | $929 |  | $825 |  | $848 |  | $94 |  | $81
Pension and OPEB costs | 371 |  | 392 |  | 187 |  | 197 |  | 184 |  | 195
Assets retired early | 282 |  | 70 |  | 267 |  | 53 |  | 15 |  | 17
Asset retirement obligations (AROs) | 199 |  | 151 |  | 155 |  | 110 |  | 44 |  | 41
Commodity cost recovery | 138 |  | 160 |  | 11 |  | 1 |  | 127 |  | 159
Derivatives | 72 |  | 84 |  | 27 |  | 48 |  | 45 |  | 36
IPL’s Duane Arnold Energy Center PPA amendment | 48 |  | 66 |  | 48 |  | 66 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 46 |  | 48 |  | — |  | — |  | 46 |  | 48
Other | 194 |  | 146 |  | 70 |  | 63 |  | 124 |  | 83
| $2,269 |  | $2,046 |  | $1,590 |  | $1,386 |  | $679 |  | $660
Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, 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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $569 |  | $579 |  | $301 |  | $303 |  | $268 |  | $276
Cost of removal obligations | 397 |  | 398 |  | 249 |  | 259 |  | 148 |  | 139
Derivatives | 91 |  | 210 |  | 52 |  | 115 |  | 39 |  | 95
Commodity cost recovery | 41 |  | 40 |  | 11 |  | 38 |  | 30 |  | 2
WPL’s West Riverside liquidated damages | 9 |  | 32 |  | — |  | — |  | 9 |  | 32
Electric transmission cost recovery | 6 |  | 20 |  | 6 |  | 10 |  | — |  | 10
Other | 74 |  | 45 |  | 36 |  | 29 |  | 38 |  | 16
| $1,187 |  | $1,324 |  | $655 |  | $754 |  | $532 |  | $570
WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.
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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $919 |  | $929 |  | $825 |  | $848 |  | $94 |  | $81
Pension and OPEB costs | 371 |  | 392 |  | 187 |  | 197 |  | 184 |  | 195
Assets retired early | 282 |  | 70 |  | 267 |  | 53 |  | 15 |  | 17
Asset retirement obligations (AROs) | 199 |  | 151 |  | 155 |  | 110 |  | 44 |  | 41
Commodity cost recovery | 138 |  | 160 |  | 11 |  | 1 |  | 127 |  | 159
Derivatives | 72 |  | 84 |  | 27 |  | 48 |  | 45 |  | 36
IPL’s Duane Arnold Energy Center PPA amendment | 48 |  | 66 |  | 48 |  | 66 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 46 |  | 48 |  | — |  | — |  | 46 |  | 48
Other | 194 |  | 146 |  | 70 |  | 63 |  | 124 |  | 83
| $2,269 |  | $2,046 |  | $1,590 |  | $1,386 |  | $679 |  | $660
Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, 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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $569 |  | $579 |  | $301 |  | $303 |  | $268 |  | $276
Cost of removal obligations | 397 |  | 398 |  | 249 |  | 259 |  | 148 |  | 139
Derivatives | 91 |  | 210 |  | 52 |  | 115 |  | 39 |  | 95
Commodity cost recovery | 41 |  | 40 |  | 11 |  | 38 |  | 30 |  | 2
WPL’s West Riverside liquidated damages | 9 |  | 32 |  | — |  | — |  | 9 |  | 32
Electric transmission cost recovery | 6 |  | 20 |  | 6 |  | 10 |  | — |  | 10
Other | 74 |  | 45 |  | 36 |  | 29 |  | 38 |  | 16
| $1,187 |  | $1,324 |  | $655 |  | $754 |  | $532 |  | $570
WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.
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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $919 |  | $929 |  | $825 |  | $848 |  | $94 |  | $81
Pension and OPEB costs | 371 |  | 392 |  | 187 |  | 197 |  | 184 |  | 195
Assets retired early | 282 |  | 70 |  | 267 |  | 53 |  | 15 |  | 17
Asset retirement obligations (AROs) | 199 |  | 151 |  | 155 |  | 110 |  | 44 |  | 41
Commodity cost recovery | 138 |  | 160 |  | 11 |  | 1 |  | 127 |  | 159
Derivatives | 72 |  | 84 |  | 27 |  | 48 |  | 45 |  | 36
IPL’s Duane Arnold Energy Center PPA amendment | 48 |  | 66 |  | 48 |  | 66 |  | — |  | —
WPL’s Western Wisconsin gas distribution expansion investments | 46 |  | 48 |  | — |  | — |  | 46 |  | 48
Other | 194 |  | 146 |  | 70 |  | 63 |  | 124 |  | 83
| $2,269 |  | $2,046 |  | $1,590 |  | $1,386 |  | $679 |  | $660
Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, 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, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022 |  | September 30, 2023 |  | December 31, 2022
Tax-related | $569 |  | $579 |  | $301 |  | $303 |  | $268 |  | $276
Cost of removal obligations | 397 |  | 398 |  | 249 |  | 259 |  | 148 |  | 139
Derivatives | 91 |  | 210 |  | 52 |  | 115 |  | 39 |  | 95
Commodity cost recovery | 41 |  | 40 |  | 11 |  | 38 |  | 30 |  | 2
WPL’s West Riverside liquidated damages | 9 |  | 32 |  | — |  | — |  | 9 |  | 32
Electric transmission cost recovery | 6 |  | 20 |  | 6 |  | 10 |  | — |  | 10
Other | 74 |  | 45 |  | 36 |  | 29 |  | 38 |  | 16
| $1,187 |  | $1,324 |  | $655 |  | $754 |  | $532 |  | $570
WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.

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