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Regulatory Matters

9 Months Ended

Sep. 30, 2025

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$1,069						$989						$932						$870						$137						$119
AROs			441						401						304						281						137						120
Pension and OPEB costs			301						315						151						157						150						158
Assets retired early			162						180						153						168						9						12
Non-service pension and OPEB costs			55						51						20						19						35						32
Derivatives			51						60						12						15						39						45
WPL’s Western Wisconsin gas distribution expansion investments			40						42						—						—						40						42
Commodity cost recovery			33						68						8						2						25						66
Other			151						168						52						74						99						94
			$2,303						$2,274						$1,632						$1,586						$671						$688

Assets retired early - IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period included a return of the remaining net book value of Lansing, but did not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value was no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024.

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$658						$582						$301						$286						$357						$296
Cost of removal obligations			351						347						206						205						145						142
Derivatives			49						53						25						29						24						24
Other			76						46						26						26						50						20
			$1,134						$1,028						$558						$546						$576						$482

Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from investment tax credits recognized by WPL for certain energy storage facilities in 2025.

IPL [Member]

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$1,069						$989						$932						$870						$137						$119
AROs			441						401						304						281						137						120
Pension and OPEB costs			301						315						151						157						150						158
Assets retired early			162						180						153						168						9						12
Non-service pension and OPEB costs			55						51						20						19						35						32
Derivatives			51						60						12						15						39						45
WPL’s Western Wisconsin gas distribution expansion investments			40						42						—						—						40						42
Commodity cost recovery			33						68						8						2						25						66
Other			151						168						52						74						99						94
			$2,303						$2,274						$1,632						$1,586						$671						$688

Assets retired early - IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period included a return of the remaining net book value of Lansing, but did not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value was no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024.

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$658						$582						$301						$286						$357						$296
Cost of removal obligations			351						347						206						205						145						142
Derivatives			49						53						25						29						24						24
Other			76						46						26						26						50						20
			$1,134						$1,028						$558						$546						$576						$482

Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from investment tax credits recognized by WPL for certain energy storage facilities in 2025.

WPL [Member]

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$1,069						$989						$932						$870						$137						$119
AROs			441						401						304						281						137						120
Pension and OPEB costs			301						315						151						157						150						158
Assets retired early			162						180						153						168						9						12
Non-service pension and OPEB costs			55						51						20						19						35						32
Derivatives			51						60						12						15						39						45
WPL’s Western Wisconsin gas distribution expansion investments			40						42						—						—						40						42
Commodity cost recovery			33						68						8						2						25						66
Other			151						168						52						74						99						94
			$2,303						$2,274						$1,632						$1,586						$671						$688

Assets retired early - IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period included a return of the remaining net book value of Lansing, but did not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value was no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024.

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

			Alliant Energy												IPL												WPL
			September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024						September 30, 2025						December 31, 2024
Tax-related			$658						$582						$301						$286						$357						$296
Cost of removal obligations			351						347						206						205						145						142
Derivatives			49						53						25						29						24						24
Other			76						46						26						26						50						20
			$1,134						$1,028						$558						$546						$576						$482

Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from investment tax credits recognized by WPL for certain energy storage facilities in 2025.

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- Definition

The entire disclosure for public utilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/980/tableOfContent

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