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Asset Retirement Obligations | 12 Months Ended
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Dec. 31, 2024
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, active and inactive ash landfills, ash ponds, wind farms, groundwater, solar facilities, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2024 |  | 2023 |  | 2024 |  | 2023
Balance, January 1 | $246 |  |  | $279 |  |  | $148 |  |  | $195 |  |  | $98 |  |  | $84 |
Revisions in estimated cash flows | (3) |  |  | (6) |  |  | (1) |  |  | (9) |  |  | (2) |  |  | 3 |
Liabilities settled | (8) |  |  | (51) |  |  | (6) |  |  | (44) |  |  | (2) |  |  | (7) |
Liabilities incurred (a) | 409 |  |  | 16 |  |  | 201 |  |  | 1 |  |  | 208 |  |  | 15 |
Accretion expense | 19 |  |  | 8 |  |  | 8 |  |  | 5 |  |  | 11 |  |  | 3 |
Balance, December 31 | $663 |  |  | $246 |  |  | $350 |  |  | $148 |  |  | $313 |  |  | $98 |
(a)In 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL initially recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts initially recorded in 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, active and inactive ash landfills, ash ponds, wind farms, groundwater, solar facilities, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2024 |  | 2023 |  | 2024 |  | 2023
Balance, January 1 | $246 |  |  | $279 |  |  | $148 |  |  | $195 |  |  | $98 |  |  | $84 |
Revisions in estimated cash flows | (3) |  |  | (6) |  |  | (1) |  |  | (9) |  |  | (2) |  |  | 3 |
Liabilities settled | (8) |  |  | (51) |  |  | (6) |  |  | (44) |  |  | (2) |  |  | (7) |
Liabilities incurred (a) | 409 |  |  | 16 |  |  | 201 |  |  | 1 |  |  | 208 |  |  | 15 |
Accretion expense | 19 |  |  | 8 |  |  | 8 |  |  | 5 |  |  | 11 |  |  | 3 |
Balance, December 31 | $663 |  |  | $246 |  |  | $350 |  |  | $148 |  |  | $313 |  |  | $98 |
(a)In 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL initially recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts initially recorded in 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations (AROs) | ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, active and inactive ash landfills, ash ponds, wind farms, groundwater, solar facilities, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2024 |  | 2023 |  | 2024 |  | 2023
Balance, January 1 | $246 |  |  | $279 |  |  | $148 |  |  | $195 |  |  | $98 |  |  | $84 |
Revisions in estimated cash flows | (3) |  |  | (6) |  |  | (1) |  |  | (9) |  |  | (2) |  |  | 3 |
Liabilities settled | (8) |  |  | (51) |  |  | (6) |  |  | (44) |  |  | (2) |  |  | (7) |
Liabilities incurred (a) | 409 |  |  | 16 |  |  | 201 |  |  | 1 |  |  | 208 |  |  | 15 |
Accretion expense | 19 |  |  | 8 |  |  | 8 |  |  | 5 |  |  | 11 |  |  | 3 |
Balance, December 31 | $663 |  |  | $246 |  |  | $350 |  |  | $148 |  |  | $313 |  |  | $98 |
(a)In 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL initially recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts initially recorded in 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.

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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/410-20/tableOfContent Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 20 -Topic 410 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-2 + Details
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