Jointly-Owned Electric Utility Plant (Tables)

12 Months Ended

Dec. 31, 2023

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):

	Ownership	Electric	Accumulated Provision	Construction
	Interest %	Plant	for Depreciation	Work in Progress
IPL
Ottumwa Unit 1	48.0%	$632	$264	$7
George Neal Unit 4	25.7%	196	107	6
George Neal Unit 3	28.0%	181	85	8
Louisa Unit 1	4.0%	44	22	—
		1,053	478	21
WPL
Columbia Units 1-2	53.5%	818	361	6
West Riverside Energy Center and Solar Facility (a)	73.8%	581	60	6
Forward Wind Energy Center	42.6%	118	53	—
		1,517	474	12
Alliant Energy		$2,570	$952	$33

(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.

IPL [Member]

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):

	Ownership	Electric	Accumulated Provision	Construction
	Interest %	Plant	for Depreciation	Work in Progress
IPL
Ottumwa Unit 1	48.0%	$632	$264	$7
George Neal Unit 4	25.7%	196	107	6
George Neal Unit 3	28.0%	181	85	8
Louisa Unit 1	4.0%	44	22	—
		1,053	478	21
WPL
Columbia Units 1-2	53.5%	818	361	6
West Riverside Energy Center and Solar Facility (a)	73.8%	581	60	6
Forward Wind Energy Center	42.6%	118	53	—
		1,517	474	12
Alliant Energy		$2,570	$952	$33

(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.

WPL [Member]

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):

	Ownership	Electric	Accumulated Provision	Construction
	Interest %	Plant	for Depreciation	Work in Progress
IPL
Ottumwa Unit 1	48.0%	$632	$264	$7
George Neal Unit 4	25.7%	196	107	6
George Neal Unit 3	28.0%	181	85	8
Louisa Unit 1	4.0%	44	22	—
		1,053	478	21
WPL
Columbia Units 1-2	53.5%	818	361	6
West Riverside Energy Center and Solar Facility (a)	73.8%	581	60	6
Forward Wind Energy Center	42.6%	118	53	—
		1,517	474	12
Alliant Energy		$2,570	$952	$33

(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.