Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2023

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
	2023	2022	2023	2022	2023	2022
Tax-related	$934	$929	$831	$848	$103	$81
Pension and OPEB costs	347	392	171	197	176	195
Assets retired early	273	70	259	53	14	17
AROs	194	151	160	110	34	41
Commodity cost recovery	120	160	12	1	108	159
Derivatives	102	84	34	48	68	36
WPL’s Western Wisconsin gas distribution expansion investments	44	48	—	—	44	48
IPL’s DAEC PPA amendment	42	66	42	66	—	—
Other	205	146	68	63	137	83
	$2,261	$2,046	$1,577	$1,386	$684	$660

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, 2023	Recovery	Regulatory Approval
IPL	Lansing	2023	$216	Return of and return on remaining net book value through 2037	FERC and pending with the IUB (a)
IPL	Analog electric meters	2019	20	Return of remaining net book value through 2028	IUB and FERC
IPL	Sutherland Units 1 and 3	2017	12	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	11	Return of and return on remaining net book value through 2029	IUB and FERC
WPL	Edgewater Unit 4	2018	14	Return of and return on remaining net book value through 2028	PSCW and FERC

(a)IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request with the IUB for continued recovery of the remaining net book value of Lansing through 2037.

Schedule of Regulatory Liabilities

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

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Tax-related	$566	$579	$299	$303	$267	$276
Cost of removal obligations	366	398	242	259	124	139
Derivatives	65	210	34	115	31	95
Commodity cost recovery	48	40	13	38	35	2
WPL’s West Riverside liquidated damages	1	32	—	—	1	32
Other	84	65	56	39	28	26
	$1,130	$1,324	$644	$754	$486	$570

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
	2023	2022	2023	2022	2023	2022
Tax-related	$934	$929	$831	$848	$103	$81
Pension and OPEB costs	347	392	171	197	176	195
Assets retired early	273	70	259	53	14	17
AROs	194	151	160	110	34	41
Commodity cost recovery	120	160	12	1	108	159
Derivatives	102	84	34	48	68	36
WPL’s Western Wisconsin gas distribution expansion investments	44	48	—	—	44	48
IPL’s DAEC PPA amendment	42	66	42	66	—	—
Other	205	146	68	63	137	83
	$2,261	$2,046	$1,577	$1,386	$684	$660

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, 2023	Recovery	Regulatory Approval
IPL	Lansing	2023	$216	Return of and return on remaining net book value through 2037	FERC and pending with the IUB (a)
IPL	Analog electric meters	2019	20	Return of remaining net book value through 2028	IUB and FERC
IPL	Sutherland Units 1 and 3	2017	12	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	11	Return of and return on remaining net book value through 2029	IUB and FERC
WPL	Edgewater Unit 4	2018	14	Return of and return on remaining net book value through 2028	PSCW and FERC

(a)IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request with the IUB for continued recovery of the remaining net book value of Lansing through 2037.

Schedule of Regulatory Liabilities

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

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Tax-related	$566	$579	$299	$303	$267	$276
Cost of removal obligations	366	398	242	259	124	139
Derivatives	65	210	34	115	31	95
Commodity cost recovery	48	40	13	38	35	2
WPL’s West Riverside liquidated damages	1	32	—	—	1	32
Other	84	65	56	39	28	26
	$1,130	$1,324	$644	$754	$486	$570

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
	2023	2022	2023	2022	2023	2022
Tax-related	$934	$929	$831	$848	$103	$81
Pension and OPEB costs	347	392	171	197	176	195
Assets retired early	273	70	259	53	14	17
AROs	194	151	160	110	34	41
Commodity cost recovery	120	160	12	1	108	159
Derivatives	102	84	34	48	68	36
WPL’s Western Wisconsin gas distribution expansion investments	44	48	—	—	44	48
IPL’s DAEC PPA amendment	42	66	42	66	—	—
Other	205	146	68	63	137	83
	$2,261	$2,046	$1,577	$1,386	$684	$660

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, 2023	Recovery	Regulatory Approval
IPL	Lansing	2023	$216	Return of and return on remaining net book value through 2037	FERC and pending with the IUB (a)
IPL	Analog electric meters	2019	20	Return of remaining net book value through 2028	IUB and FERC
IPL	Sutherland Units 1 and 3	2017	12	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	11	Return of and return on remaining net book value through 2029	IUB and FERC
WPL	Edgewater Unit 4	2018	14	Return of and return on remaining net book value through 2028	PSCW and FERC

(a)IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request with the IUB for continued recovery of the remaining net book value of Lansing through 2037.

Schedule of Regulatory Liabilities

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

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Tax-related	$566	$579	$299	$303	$267	$276
Cost of removal obligations	366	398	242	259	124	139
Derivatives	65	210	34	115	31	95
Commodity cost recovery	48	40	13	38	35	2
WPL’s West Riverside liquidated damages	1	32	—	—	1	32
Other	84	65	56	39	28	26
	$1,130	$1,324	$644	$754	$486	$570