Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2024

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

Components of regulatory assets:

(Millions of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2024				Dec. 31, 2023
Regulatory Assets			Current		Noncurrent		Current		Noncurrent
Pension and retiree medical obligations	9	Various	$	2	$	60	$	2	$	62
Environmental remediation costs	1, 10	Various	13		34		13		48
Recoverable deferred taxes on AFUDC		Plant lives	—		31		—		26
State commission adjustments		Plant lives	1		21		1		22
Net AROs (a)	1, 10	Various	—		21		—		21
Other		Various	7		1		8		6
Total regulatory assets			$	23	$	168	$	24	$	185

(a)Includes amounts recorded for future recovery of AROs and NSP-Wisconsin’s share of nuclear decommissioning accruals.

Regulatory Liabilities

Components of regulatory liabilities:

(Millions of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2024				Dec. 31, 2023
Regulatory Liabilities			Current		Noncurrent		Current		Noncurrent
Plant removal costs	1, 10	Various	$	—	$	276	$	—	$	251
Deferred income tax adjustments and TCJA refunds (a)	7	Various	—		134		—		140
IRA deferral		One to three years	3		37		—		—
DOE Settlement		One to two years	4		4		4		6
Deferred natural gas and electric energy/fuel costs		Less than one year	13		—		28		—
Other		Various	9		5		10		10
Total regulatory liabilities			$	29	$	456	$	42	$	407

(a)Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA.

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[1] Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA.