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Property, Plant and Equipment (Tables) | 12 Months Ended
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Dec. 31, 2023
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2023 |  | 2022 |  | 2023 |  | 2022
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service (a) | $9,180 |  |  | $8,060 |  |  | $5,025 |  |  | $4,962 |  |  | $4,155 |  |  | $3,098 |
Distribution in service | 7,314 |  |  | 6,912 |  |  | 4,091 |  |  | 3,876 |  |  | 3,223 |  |  | 3,036 |
Other in service | 567 |  |  | 543 |  |  | 356 |  |  | 354 |  |  | 211 |  |  | 189 |
Anticipated to be retired early (b) | 1,629 |  |  | 2,103 |  |  | — |  |  | 491 |  |  | 1,629 |  |  | 1,612 |
Total electric plant | 18,690 |  |  | 17,618 |  |  | 9,472 |  |  | 9,683 |  |  | 9,218 |  |  | 7,935 |
Gas plant in service | 1,791 |  |  | 1,705 |  |  | 951 |  | 910 |  |  | 840 |  |  | 795 |
Other plant in service | 653 |  |  | 624 |  |  | 411 |  | 402 |  |  | 242 |  |  | 222 |
Accumulated depreciation (b) | (5,924) |  |  | (5,690) |  |  | (3,180) |  |  | (3,149) |  |  | (2,744) |  |  | (2,541) |
Net plant | 15,210 |  |  | 14,257 |  |  | 7,654 |  |  | 7,846 |  |  | 7,556 |  |  | 6,411 |
Leased Sheboygan Falls Energy Facility, net (c) | — |  |  | — |  |  | — |  |  | — |  |  | 79 |  |  | 15 |
Leased land for solar generation, net | 172 |  |  | 133 |  |  | 33 |  |  | — |  |  | 139 |  |  | 133 |
Construction work in progress | 1,245 |  |  | 1,357 |  |  | 605 |  | 194 |  |  | 640 |  |  | 1,163 |
Other, net | 7 |  |  | 6 |  |  | 6 |  |  | 6 |  |  | 1 |  |  | — |
Total utility | 16,634 |  |  | 15,753 |  |  | 8,298 |  |  | 8,046 |  |  | 8,415 |  |  | 7,722 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (d) | 68 |  |  | 71 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (e) | 455 |  | 423 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 523 |  |  | 494 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment | $17,157 |  |  | $16,247 |  |  | $8,298 |  |  | $8,046 |  |  | $8,415 |  |  | $7,722 |
(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred. (b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate. (c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively. (e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Equity | $74 |  | $44 |  | $18 |  | $15 |  | $8 |  | $7 |  | $59 |  | $36 |  | $11
Debt | 26 |  | 16 |  | 7 |  | 6 |  | 3 |  | 2 |  | 20 |  | 13 |  | 5
| $100 |  | $60 |  | $25 |  | $21 |  | $11 |  | $9 |  | $79 |  | $49 |  | $16
IPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2023 |  | 2022 |  | 2023 |  | 2022
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service (a) | $9,180 |  |  | $8,060 |  |  | $5,025 |  |  | $4,962 |  |  | $4,155 |  |  | $3,098 |
Distribution in service | 7,314 |  |  | 6,912 |  |  | 4,091 |  |  | 3,876 |  |  | 3,223 |  |  | 3,036 |
Other in service | 567 |  |  | 543 |  |  | 356 |  |  | 354 |  |  | 211 |  |  | 189 |
Anticipated to be retired early (b) | 1,629 |  |  | 2,103 |  |  | — |  |  | 491 |  |  | 1,629 |  |  | 1,612 |
Total electric plant | 18,690 |  |  | 17,618 |  |  | 9,472 |  |  | 9,683 |  |  | 9,218 |  |  | 7,935 |
Gas plant in service | 1,791 |  |  | 1,705 |  |  | 951 |  | 910 |  |  | 840 |  |  | 795 |
Other plant in service | 653 |  |  | 624 |  |  | 411 |  | 402 |  |  | 242 |  |  | 222 |
Accumulated depreciation (b) | (5,924) |  |  | (5,690) |  |  | (3,180) |  |  | (3,149) |  |  | (2,744) |  |  | (2,541) |
Net plant | 15,210 |  |  | 14,257 |  |  | 7,654 |  |  | 7,846 |  |  | 7,556 |  |  | 6,411 |
Leased Sheboygan Falls Energy Facility, net (c) | — |  |  | — |  |  | — |  |  | — |  |  | 79 |  |  | 15 |
Leased land for solar generation, net | 172 |  |  | 133 |  |  | 33 |  |  | — |  |  | 139 |  |  | 133 |
Construction work in progress | 1,245 |  |  | 1,357 |  |  | 605 |  | 194 |  |  | 640 |  |  | 1,163 |
Other, net | 7 |  |  | 6 |  |  | 6 |  |  | 6 |  |  | 1 |  |  | — |
Total utility | 16,634 |  |  | 15,753 |  |  | 8,298 |  |  | 8,046 |  |  | 8,415 |  |  | 7,722 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (d) | 68 |  |  | 71 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (e) | 455 |  | 423 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 523 |  |  | 494 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment | $17,157 |  |  | $16,247 |  |  | $8,298 |  |  | $8,046 |  |  | $8,415 |  |  | $7,722 |
(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred. (b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate. (c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively. (e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Equity | $74 |  | $44 |  | $18 |  | $15 |  | $8 |  | $7 |  | $59 |  | $36 |  | $11
Debt | 26 |  | 16 |  | 7 |  | 6 |  | 3 |  | 2 |  | 20 |  | 13 |  | 5
| $100 |  | $60 |  | $25 |  | $21 |  | $11 |  | $9 |  | $79 |  | $49 |  | $16
WPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2023 |  | 2022 |  | 2023 |  | 2022
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service (a) | $9,180 |  |  | $8,060 |  |  | $5,025 |  |  | $4,962 |  |  | $4,155 |  |  | $3,098 |
Distribution in service | 7,314 |  |  | 6,912 |  |  | 4,091 |  |  | 3,876 |  |  | 3,223 |  |  | 3,036 |
Other in service | 567 |  |  | 543 |  |  | 356 |  |  | 354 |  |  | 211 |  |  | 189 |
Anticipated to be retired early (b) | 1,629 |  |  | 2,103 |  |  | — |  |  | 491 |  |  | 1,629 |  |  | 1,612 |
Total electric plant | 18,690 |  |  | 17,618 |  |  | 9,472 |  |  | 9,683 |  |  | 9,218 |  |  | 7,935 |
Gas plant in service | 1,791 |  |  | 1,705 |  |  | 951 |  | 910 |  |  | 840 |  |  | 795 |
Other plant in service | 653 |  |  | 624 |  |  | 411 |  | 402 |  |  | 242 |  |  | 222 |
Accumulated depreciation (b) | (5,924) |  |  | (5,690) |  |  | (3,180) |  |  | (3,149) |  |  | (2,744) |  |  | (2,541) |
Net plant | 15,210 |  |  | 14,257 |  |  | 7,654 |  |  | 7,846 |  |  | 7,556 |  |  | 6,411 |
Leased Sheboygan Falls Energy Facility, net (c) | — |  |  | — |  |  | — |  |  | — |  |  | 79 |  |  | 15 |
Leased land for solar generation, net | 172 |  |  | 133 |  |  | 33 |  |  | — |  |  | 139 |  |  | 133 |
Construction work in progress | 1,245 |  |  | 1,357 |  |  | 605 |  | 194 |  |  | 640 |  |  | 1,163 |
Other, net | 7 |  |  | 6 |  |  | 6 |  |  | 6 |  |  | 1 |  |  | — |
Total utility | 16,634 |  |  | 15,753 |  |  | 8,298 |  |  | 8,046 |  |  | 8,415 |  |  | 7,722 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (d) | 68 |  |  | 71 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (e) | 455 |  | 423 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 523 |  |  | 494 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment | $17,157 |  |  | $16,247 |  |  | $8,298 |  |  | $8,046 |  |  | $8,415 |  |  | $7,722 |
(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred. (b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate. (c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively. (e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Equity | $74 |  | $44 |  | $18 |  | $15 |  | $8 |  | $7 |  | $59 |  | $36 |  | $11
Debt | 26 |  | 16 |  | 7 |  | 6 |  | 3 |  | 2 |  | 20 |  | 13 |  | 5
| $100 |  | $60 |  | $25 |  | $21 |  | $11 |  | $9 |  | $79 |  | $49 |  | $16

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- Definition Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 10 -Topic 360 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482099/360-10-50-1 + Details
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