Regulatory Matters (Tables)

3 Months Ended

Mar. 31, 2024

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$939	$934	$839	$831	$100	$103
Pension and OPEB costs	340	347	168	171	172	176
Assets retired early	267	273	253	259	14	14
Asset retirement obligations (AROs)	200	194	165	160	35	34
Commodity cost recovery	100	120	5	12	95	108
Derivatives	97	102	33	34	64	68
WPL’s Western Wisconsin gas distribution expansion investments	44	44	—	—	44	44
IPL’s Duane Arnold Energy Center PPA amendment	36	42	36	42	—	—
Other	197	205	68	68	129	137
	$2,220	$2,261	$1,567	$1,577	$653	$684

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$563	$566	$297	$299	$266	$267
Cost of removal obligations	380	366	241	242	139	124
Derivatives	49	65	28	34	21	31
Commodity cost recovery	61	48	25	13	36	35
Other	83	85	57	56	26	29
	$1,136	$1,130	$648	$644	$488	$486

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$939	$934	$839	$831	$100	$103
Pension and OPEB costs	340	347	168	171	172	176
Assets retired early	267	273	253	259	14	14
Asset retirement obligations (AROs)	200	194	165	160	35	34
Commodity cost recovery	100	120	5	12	95	108
Derivatives	97	102	33	34	64	68
WPL’s Western Wisconsin gas distribution expansion investments	44	44	—	—	44	44
IPL’s Duane Arnold Energy Center PPA amendment	36	42	36	42	—	—
Other	197	205	68	68	129	137
	$2,220	$2,261	$1,567	$1,577	$653	$684

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$563	$566	$297	$299	$266	$267
Cost of removal obligations	380	366	241	242	139	124
Derivatives	49	65	28	34	21	31
Commodity cost recovery	61	48	25	13	36	35
Other	83	85	57	56	26	29
	$1,136	$1,130	$648	$644	$488	$486

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$939	$934	$839	$831	$100	$103
Pension and OPEB costs	340	347	168	171	172	176
Assets retired early	267	273	253	259	14	14
Asset retirement obligations (AROs)	200	194	165	160	35	34
Commodity cost recovery	100	120	5	12	95	108
Derivatives	97	102	33	34	64	68
WPL’s Western Wisconsin gas distribution expansion investments	44	44	—	—	44	44
IPL’s Duane Arnold Energy Center PPA amendment	36	42	36	42	—	—
Other	197	205	68	68	129	137
	$2,220	$2,261	$1,567	$1,577	$653	$684

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy		IPL		WPL
	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023	March 31, 2024	December 31, 2023
Tax-related	$563	$566	$297	$299	$266	$267
Cost of removal obligations	380	366	241	242	139	124
Derivatives	49	65	28	34	21	31
Commodity cost recovery	61	48	25	13	36	35
Other	83	85	57	56	26	29
	$1,136	$1,130	$648	$644	$488	$486