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Regulatory Matters (Tables)
 12 Months Ended
Dec. 31, 2021
Regulatory Assets [Line Items]  
Schedule of Regulatory Assets At December 31, regulatory assets were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$934 $890 $884 $843 $50 $47 
Pension and OPEB costs462 580 228 291 234 289 
AROs128 119 89 81 39 38 
Assets retired early92 113 66 77 26 36 
IPL’s DAEC PPA amendment90 110 90 110 — — 
WPL’s Western Wisconsin gas distribution expansion investments52 55 — — 52 55 
Commodity cost recovery42 4 2 1 40 3 
Derivatives8 26 4 13 4 13 
Other132 113 80 67 52 46 
$1,940 $2,010 $1,443 $1,483 $497 $527 
Schedule of Assets Retired Early Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions):
EntityAssetRetirement DateRegulatory Asset Balance as of Dec. 31, 2021RecoveryRegulatory Approval
IPLSutherland Units 1 and 32017$19Return of and return on remaining net book value through 2027IUB and FERC
IPLM.L. Kapp Unit 2201818Return of and return on remaining net book value through 2029IUB and FERC
IPLAnalog electric meters201929Return of remaining net book value through 2028IUB and FERC
WPLNelson Dewey Units 1 and 2 and Edgewater Unit 320156Return of and return on remaining net book value through 2022PSCW and FERC
WPLEdgewater Unit 4201820Return of and return on remaining net book value through 2028PSCW and FERC
Schedule of Regulatory Liabilities At December 31, regulatory liabilities were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$585$732$312$331$273$401
Cost of removal obligations384367252238132129
Derivatives166287725893
Electric transmission cost recovery516827392429
WPL’s West Riverside liquidated damages3638——3638
Other497323432630
$1,271$1,306$691$676$580$630
IPL [Member]  
Regulatory Assets [Line Items]  
Schedule of Regulatory Assets At December 31, regulatory assets were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$934 $890 $884 $843 $50 $47 
Pension and OPEB costs462 580 228 291 234 289 
AROs128 119 89 81 39 38 
Assets retired early92 113 66 77 26 36 
IPL’s DAEC PPA amendment90 110 90 110 — — 
WPL’s Western Wisconsin gas distribution expansion investments52 55 — — 52 55 
Commodity cost recovery42 4 2 1 40 3 
Derivatives8 26 4 13 4 13 
Other132 113 80 67 52 46 
$1,940 $2,010 $1,443 $1,483 $497 $527 
Schedule of Assets Retired Early Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions):
EntityAssetRetirement DateRegulatory Asset Balance as of Dec. 31, 2021RecoveryRegulatory Approval
IPLSutherland Units 1 and 32017$19Return of and return on remaining net book value through 2027IUB and FERC
IPLM.L. Kapp Unit 2201818Return of and return on remaining net book value through 2029IUB and FERC
IPLAnalog electric meters201929Return of remaining net book value through 2028IUB and FERC
WPLNelson Dewey Units 1 and 2 and Edgewater Unit 320156Return of and return on remaining net book value through 2022PSCW and FERC
WPLEdgewater Unit 4201820Return of and return on remaining net book value through 2028PSCW and FERC
Schedule of Regulatory Liabilities At December 31, regulatory liabilities were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$585$732$312$331$273$401
Cost of removal obligations384367252238132129
Derivatives166287725893
Electric transmission cost recovery516827392429
WPL’s West Riverside liquidated damages3638——3638
Other497323432630
$1,271$1,306$691$676$580$630
WPL [Member]  
Regulatory Assets [Line Items]  
Schedule of Regulatory Assets At December 31, regulatory assets were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$934 $890 $884 $843 $50 $47 
Pension and OPEB costs462 580 228 291 234 289 
AROs128 119 89 81 39 38 
Assets retired early92 113 66 77 26 36 
IPL’s DAEC PPA amendment90 110 90 110 — — 
WPL’s Western Wisconsin gas distribution expansion investments52 55 — — 52 55 
Commodity cost recovery42 4 2 1 40 3 
Derivatives8 26 4 13 4 13 
Other132 113 80 67 52 46 
$1,940 $2,010 $1,443 $1,483 $497 $527 
Schedule of Assets Retired Early Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions):
EntityAssetRetirement DateRegulatory Asset Balance as of Dec. 31, 2021RecoveryRegulatory Approval
IPLSutherland Units 1 and 32017$19Return of and return on remaining net book value through 2027IUB and FERC
IPLM.L. Kapp Unit 2201818Return of and return on remaining net book value through 2029IUB and FERC
IPLAnalog electric meters201929Return of remaining net book value through 2028IUB and FERC
WPLNelson Dewey Units 1 and 2 and Edgewater Unit 320156Return of and return on remaining net book value through 2022PSCW and FERC
WPLEdgewater Unit 4201820Return of and return on remaining net book value through 2028PSCW and FERC
Schedule of Regulatory Liabilities At December 31, regulatory liabilities were comprised of the following items (in millions):
Alliant EnergyIPLWPL
202120202021202020212020
Tax-related$585$732$312$331$273$401
Cost of removal obligations384367252238132129
Derivatives166287725893
Electric transmission cost recovery516827392429
WPL’s West Riverside liquidated damages3638——3638
Other497323432630
$1,271$1,306$691$676$580$630