Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2020

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$890	$818	$843	$777	$47	$41
Pension and OPEB costs	580	524	291	263	289	261
AROs	119	112	81	76	38	36
Assets retired early	113	134	77	88	36	46
IPL’s DAEC PPA amendment	110	108	110	108	—	—
WPL’s Western Wisconsin gas distribution expansion investments	55	—	—	—	55	—
Derivatives	26	39	13	18	13	21
Other	117	110	68	70	49	40
	$2,010	$1,845	$1,483	$1,400	$527	$445

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):

Entity	Asset	Retirement Date	Regulatory Asset Balance as of Dec. 31, 2020	Recovery	Regulatory Approval
IPL	Sutherland Units 1 and 3	2017	$23	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	21	Return of and return on remaining net book value through 2029	IUB and FERC
IPL	Analog electric meters	2019	33	Return of remaining net book value through 2028	IUB and FERC
WPL	Nelson Dewey Units 1 and 2 and Edgewater Unit 3	2015	13	Return of and return on remaining net book value through 2022	PSCW and FERC
WPL	Edgewater Unit 4	2018	23	Return of and return on remaining net book value through 2028	PSCW and FERC

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$732	$836	$331	$351	$401	$485
Cost of removal obligations	367	388	238	257	129	131
Electric transmission cost recovery	68	88	39	51	29	37
WPL’s West Riverside liquidated damages	38	—	—	—	38	—
Derivatives	28	20	25	17	3	3
Other	73	92	43	39	30	53
	$1,306	$1,424	$676	$715	$630	$709

IPL [Member]

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$890	$818	$843	$777	$47	$41
Pension and OPEB costs	580	524	291	263	289	261
AROs	119	112	81	76	38	36
Assets retired early	113	134	77	88	36	46
IPL’s DAEC PPA amendment	110	108	110	108	—	—
WPL’s Western Wisconsin gas distribution expansion investments	55	—	—	—	55	—
Derivatives	26	39	13	18	13	21
Other	117	110	68	70	49	40
	$2,010	$1,845	$1,483	$1,400	$527	$445

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):

Entity	Asset	Retirement Date	Regulatory Asset Balance as of Dec. 31, 2020	Recovery	Regulatory Approval
IPL	Sutherland Units 1 and 3	2017	$23	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	21	Return of and return on remaining net book value through 2029	IUB and FERC
IPL	Analog electric meters	2019	33	Return of remaining net book value through 2028	IUB and FERC
WPL	Nelson Dewey Units 1 and 2 and Edgewater Unit 3	2015	13	Return of and return on remaining net book value through 2022	PSCW and FERC
WPL	Edgewater Unit 4	2018	23	Return of and return on remaining net book value through 2028	PSCW and FERC

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$732	$836	$331	$351	$401	$485
Cost of removal obligations	367	388	238	257	129	131
Electric transmission cost recovery	68	88	39	51	29	37
WPL’s West Riverside liquidated damages	38	—	—	—	38	—
Derivatives	28	20	25	17	3	3
Other	73	92	43	39	30	53
	$1,306	$1,424	$676	$715	$630	$709

WPL [Member]

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$890	$818	$843	$777	$47	$41
Pension and OPEB costs	580	524	291	263	289	261
AROs	119	112	81	76	38	36
Assets retired early	113	134	77	88	36	46
IPL’s DAEC PPA amendment	110	108	110	108	—	—
WPL’s Western Wisconsin gas distribution expansion investments	55	—	—	—	55	—
Derivatives	26	39	13	18	13	21
Other	117	110	68	70	49	40
	$2,010	$1,845	$1,483	$1,400	$527	$445

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):

Entity	Asset	Retirement Date	Regulatory Asset Balance as of Dec. 31, 2020	Recovery	Regulatory Approval
IPL	Sutherland Units 1 and 3	2017	$23	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	21	Return of and return on remaining net book value through 2029	IUB and FERC
IPL	Analog electric meters	2019	33	Return of remaining net book value through 2028	IUB and FERC
WPL	Nelson Dewey Units 1 and 2 and Edgewater Unit 3	2015	13	Return of and return on remaining net book value through 2022	PSCW and FERC
WPL	Edgewater Unit 4	2018	23	Return of and return on remaining net book value through 2028	PSCW and FERC

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Tax-related	$732	$836	$331	$351	$401	$485
Cost of removal obligations	367	388	238	257	129	131
Electric transmission cost recovery	68	88	39	51	29	37
WPL’s West Riverside liquidated damages	38	—	—	—	38	—
Derivatives	28	20	25	17	3	3
Other	73	92	43	39	30	53
	$1,306	$1,424	$676	$715	$630	$709