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Income Taxes (Tables)
 9 Months Ended
Sep. 30, 2022
Income Taxes [Line Items]  
Schedule Of Effective Income Tax Rates Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three
and nine months ended September 30, 2022 compared to the same periods in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
Alliant EnergyIPLWPL
Three MonthsNine Months Three MonthsNine Months Three MonthsNine Months
202220212022202120222021202220212022202120222021
Overall income tax rate6%(9%)4%(13%)(12%)(8%)(14%)(11%)15%(19%)17%(24%)
Summary Of Tax Credit Carryforwards At September 30, 2022, the remaining carryforwards and expiration dates were estimated as follows (in millions):
Range of Expiration DatesAlliant EnergyIPLWPL
State net operating losses2022-2042$500$9$2
Federal tax credits2022-2042655437208
IPL [Member]  
Income Taxes [Line Items]  
Schedule Of Effective Income Tax Rates Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three
and nine months ended September 30, 2022 compared to the same periods in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
Alliant EnergyIPLWPL
Three MonthsNine Months Three MonthsNine Months Three MonthsNine Months
202220212022202120222021202220212022202120222021
Overall income tax rate6%(9%)4%(13%)(12%)(8%)(14%)(11%)15%(19%)17%(24%)
Summary Of Tax Credit Carryforwards At September 30, 2022, the remaining carryforwards and expiration dates were estimated as follows (in millions):
Range of Expiration DatesAlliant EnergyIPLWPL
State net operating losses2022-2042$500$9$2
Federal tax credits2022-2042655437208
WPL [Member]  
Income Taxes [Line Items]  
Schedule Of Effective Income Tax Rates Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three
and nine months ended September 30, 2022 compared to the same periods in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
Alliant EnergyIPLWPL
Three MonthsNine Months Three MonthsNine Months Three MonthsNine Months
202220212022202120222021202220212022202120222021
Overall income tax rate6%(9%)4%(13%)(12%)(8%)(14%)(11%)15%(19%)17%(24%)
Summary Of Tax Credit Carryforwards At September 30, 2022, the remaining carryforwards and expiration dates were estimated as follows (in millions):
Range of Expiration DatesAlliant EnergyIPLWPL
State net operating losses2022-2042$500$9$2
Federal tax credits2022-2042655437208