PROPERTY, PLANT AND EQUIPMENT

At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Utility:
Electric plant:
Generation in service (a)	$9,180	$8,060	$5,025	$4,962	$4,155	$3,098
Distribution in service	7,314	6,912	4,091	3,876	3,223	3,036
Other in service	567	543	356	354	211	189
Anticipated to be retired early (b)	1,629	2,103	—	491	1,629	1,612
Total electric plant	18,690	17,618	9,472	9,683	9,218	7,935
Gas plant in service	1,791	1,705	951	910	840	795
Other plant in service	653	624	411	402	242	222
Accumulated depreciation (b)	(5,924)	(5,690)	(3,180)	(3,149)	(2,744)	(2,541)
Net plant	15,210	14,257	7,654	7,846	7,556	6,411
Leased Sheboygan Falls Energy Facility, net (c)	—	—	—	—	79	15
Leased land for solar generation, net	172	133	33	—	139	133
Construction work in progress	1,245	1,357	605	194	640	1,163
Other, net	7	6	6	6	1	—
Total utility	16,634	15,753	8,298	8,046	8,415	7,722
Non-utility and other:
Non-utility Generation, net (d)	68	71	—	—	—	—
Corporate Services and other, net (e)	455	423	—	—	—	—
Total non-utility and other	523	494	—	—	—	—
Total property, plant and equipment	$17,157	$16,247	$8,298	$8,046	$8,415	$7,722

(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred.

(b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate.

(c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.

(d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

(e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Equity	$74	$44	$18	$15	$8	$7	$59	$36	$11
Debt	26	16	7	6	3	2	20	13	5
	$100	$60	$25	$21	$11	$9	$79	$49	$16

Non-utility and Other - The non-utility and other property, plant and equipment recorded on Alliant Energy’s balance sheets include the following:

Non-utility Generation - The Sheboygan Falls Energy Facility was placed in service in 2005 and is depreciated using the straight-line method over a 35-year period.

Corporate Services and Other - Property, plant and equipment related to Corporate Services include a customer billing and information system for IPL and WPL and other computer software, and the corporate headquarters building located in Madison, Wisconsin. The customer billing and information system is amortized using the straight-line method over a 12-year period. The majority of the remaining software is amortized over a 5-year period. Other property, plant and equipment include Travero assets (a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; wind turbine blade recycling services; and a rail-served warehouse in Iowa). All Corporate Services and Other property, plant and equipment are depreciated using the straight-line method over periods ranging from 5 to 30 years.

Property, Plant and Equipment [Line Items]

Property, Plant and Equipment

PROPERTY, PLANT AND EQUIPMENT

At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Utility:
Electric plant:
Generation in service (a)	$9,180	$8,060	$5,025	$4,962	$4,155	$3,098
Distribution in service	7,314	6,912	4,091	3,876	3,223	3,036
Other in service	567	543	356	354	211	189
Anticipated to be retired early (b)	1,629	2,103	—	491	1,629	1,612
Total electric plant	18,690	17,618	9,472	9,683	9,218	7,935
Gas plant in service	1,791	1,705	951	910	840	795
Other plant in service	653	624	411	402	242	222
Accumulated depreciation (b)	(5,924)	(5,690)	(3,180)	(3,149)	(2,744)	(2,541)
Net plant	15,210	14,257	7,654	7,846	7,556	6,411
Leased Sheboygan Falls Energy Facility, net (c)	—	—	—	—	79	15
Leased land for solar generation, net	172	133	33	—	139	133
Construction work in progress	1,245	1,357	605	194	640	1,163
Other, net	7	6	6	6	1	—
Total utility	16,634	15,753	8,298	8,046	8,415	7,722
Non-utility and other:
Non-utility Generation, net (d)	68	71	—	—	—	—
Corporate Services and other, net (e)	455	423	—	—	—	—
Total non-utility and other	523	494	—	—	—	—
Total property, plant and equipment	$17,157	$16,247	$8,298	$8,046	$8,415	$7,722

(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred.

(b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate.

(c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.

(d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

(e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Equity	$74	$44	$18	$15	$8	$7	$59	$36	$11
Debt	26	16	7	6	3	2	20	13	5
	$100	$60	$25	$21	$11	$9	$79	$49	$16