Northern States Power 10-Q 31 Oct 24 2024 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2024	Oct. 31, 2024
Cover [Abstract]
Entity Registrant Name	NORTHERN STATES POWER CO /WI/
Entity Central Index Key	0000072909
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-03140
Entity Incorporation, State or Country Code	WI
Entity Tax Identification Number	39-0508315
Entity Address, Address Line One	1414 West Hamilton Avenue
Entity Address, City or Town	Eau Claire
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	54701
City Area Code	(715)
Local Phone Number	852-5812
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		933,000

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating revenues
Electric, non-affiliates	$ 225	$ 213	$ 620	$ 602
Related Party Transaction, Electric Domestic Regulated Revenue	53	50	160	151
Natural gas	17	15	92	116
Other	0	1	0	1
Total operating revenues	295	279	872	870
Operating expenses
Electric fuel and purchased power, non-affiliates	3	3	10	10
Purchased power, affiliates	109	109	314	305
Cost of natural sold and transported	6	6	37	61
Operating and maintenance expenses	55	58	170	173
Conservation program expenses	3	3	9	10
Depreciation and amortization	47	43	138	126
Taxes (other than income taxes)	9	8	26	25
Total operating expenses	232	230	704	710
Operating income	63	49	168	160
Other income, net	3	1	4	2
Allowance for funds used during construction — equity	4	3	11	7
Interest charges and financing costs
Interest charges and other financing costs	19	14	50	40
Allowance for funds used during construction — debt	(2)	(1)	(5)	(3)
Total interest charges and financing costs	17	13	45	37
Income before income taxes	53	40	138	132
Income tax expense	12	9	31	30
Net income	$ 41	$ 31	$ 107	$ 102

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Operating activities
Net income	$ 107	$ 102
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	140	128
Deferred income taxes	(2)	(17)
Allowance for equity funds used during construction	11	7
Provision for bad debts	2	3
Changes in operating assets and liabilities:
Accounts receivable	10	1
Accrued unbilled revenues	4	23
Inventories	(9)	4
Other current assets	8	28
Accounts payable	14	12
Net regulatory assets and liabilities	6	61
Other current liabilities	12	3
Pension and other employee benefit obligations	(8)	(2)
Other, net	5	4
Net cash provided by operating activities	278	343
Investing activities
Capital/construction expenditures	(394)	(343)
Investments in utility money pool arrangement	0	(88)
Repayments from utility money pool arrangement	0	88
Net cash used in investing activities	(394)	(343)
Financing activities
Proceeds from long-term debt	394	124
Repayments of Long-term Debt	(200)	0
Repayments of short-term borrowings, net	(60)	(47)
Borrowings under utility money pool arrangement	170	73
Repayments under utility money pool arrangement	(170)	(73)
Capital contributions from parent	191	57
Dividends paid to parent	(72)	(72)
Net cash provided by financing activities	253	62
Net change in cash, cash equivalents and restricted cash	137	62
Cash, cash equivalents and restricted cash at beginning of period	6	2
Cash, cash equivalents and restricted cash at end of period	143	64
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(34)	(34)
Cash paid for income taxes, net	(25)	(30)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	41	31
Inventory transfers to property, plant and equipment	11	5
Allowance for equity funds used during construction	$ 11	$ 7

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 143	$ 6
Accounts receivable, net	69	89
Accrued unbilled revenues	58	63
Inventories	28	29
Regulatory assets	23	24
Prepaid taxes	22	28
Prepayments and other	4	6
Total current assets	347	245
Property, Plant and Equipment, Net [Abstract]
Property, plant and equipment, net	3,553	3,237
Other assets
Regulatory assets	172	185
Other	4	3
Total other assets	176	188
Total assets	4,076	3,670
Current liabilities
Current portion of long-term debt	0	200
Short-term debt	0	60
Dividends payable to parent	16	25
Regulatory liabilities	48	42
Taxes accrued	15	16
Accrued interest	20	13
Other	28	23
Total current liabilities	226	464
Deferred credits and other liabilities
Deferred income taxes	338	330
Deferred investment tax credits	4	5
Regulatory liabilities	415	407
Customer advances	30	25
Pension and employee benefit obligations	21	27
Other	37	35
Total deferred credits and other liabilities	845	829
Commitments and contingencies
Capitalization
Long-term debt	1,405	1,011
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at Sept. 30, 2024 and Dec. 31, 2023, respectively	$ 93	$ 93
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, par value (in dollars per share)	$ 100	$ 100
Common stock, shares outstanding (in shares)	933,000	933,000
Additional paid in capital	$ 1,033	$ 843
Retained earnings	474	430
Total common stockholder's equity	1,600	1,366
Total liabilities and equity	4,076	3,670
Related Party
Current liabilities
Accounts payable	72	64
Affiliated Entity
Current liabilities
Accounts payable	$ 27	$ 21

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common stock	Additional Paid In Capital	Retained Earnings
Balance (in shares) at Dec. 31, 2022		933,000
Beginning Balance at Dec. 31, 2022	$ 1,259	$ 93	$ 761	$ 405
Increase (Decrease) in Stockholder's Equity
Net income	102
Common dividends declared to parent	(73)			(73)
Contribution of capital by parent	59		59
Balance (in shares) at Sep. 30, 2023		933,000
Ending Balance at Sep. 30, 2023	1,347	$ 93	820	434
Balance (in shares) at Jun. 30, 2023		933,000
Beginning Balance at Jun. 30, 2023	1,326	$ 93	806	427
Increase (Decrease) in Stockholder's Equity
Net income	31			31
Common dividends declared to parent	(24)			(24)
Contribution of capital by parent	14		14
Balance (in shares) at Sep. 30, 2023		933,000
Ending Balance at Sep. 30, 2023	$ 1,347	$ 93	820	434
Balance (in shares) at Dec. 31, 2023	933,000	933,000
Beginning Balance at Dec. 31, 2023	$ 1,366	$ 93	843	430
Increase (Decrease) in Stockholder's Equity
Net income	107
Common dividends declared to parent	(63)			(63)
Contribution of capital by parent	$ 190		190
Balance (in shares) at Sep. 30, 2024	933,000	933,000
Ending Balance at Sep. 30, 2024	$ 1,600	$ 93	1,033	474
Balance (in shares) at Jun. 30, 2024		933,000
Beginning Balance at Jun. 30, 2024	1,579	$ 93	1,026	460
Increase (Decrease) in Stockholder's Equity
Net income	41			41
Common dividends declared to parent	(27)			(27)
Contribution of capital by parent	$ 7		7
Balance (in shares) at Sep. 30, 2024	933,000	933,000
Ending Balance at Sep. 30, 2024	$ 1,600	$ 93	$ 1,033	$ 474

Management's Opinion

Management's Opinion	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Opinion	In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly, in accordance with GAAP, the financial position of NSP-Wisconsin and its subsidiaries as of Sept. 30, 2024 and Dec. 31, 2023; the results of NSP-Wisconsin's operations, including the components of net income and changes in stockholder's equity for the three and nine months ended Sept. 30, 2024 and 2023; and NSP-Wisconsin’s cash flows for the nine months ended Sept. 30, 2024 and 2023. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after Sept. 30, 2024 up to the date of issuance of these consolidated financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. The Dec. 31, 2023 balance sheet information has been derived from the audited 2023 consolidated financial statements included in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2023. Notes to the consolidated financial statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP on an annual basis have been condensed or omitted pursuant to such rules and regulations. For further information, refer to the consolidated financial statements and notes thereto included in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2023, filed with the SEC on Feb. 21, 2024. Due to the seasonality of NSP-Wisconsin’s electric and natural gas sales, interim results are not necessarily an appropriate base from which to project annual results.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies The significant accounting policies set forth in Note 1 to the consolidated financial statements in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2023 appropriately represent, in all material respects, the current status of accounting policies and are incorporated herein by reference.

Accounting Pronouncements

Accounting Pronouncements	9 Months Ended
	Sep. 30, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Pronouncements	Recently Issued Segment Reporting — In November 2023, the FASB issued ASU 2023-07 – Segment Reporting (Topic 280) – Improvements to Reportable Segment Disclosures , which extends the existing requirements for annual disclosures to quarterly periods, and requires that both annual and quarterly disclosures present segment expenses using line items consistent with information regularly provided to the chief operating decision maker. The ASU is effective for annual periods beginning after Dec. 15, 2023 and quarterly periods beginning after Dec. 15, 2024, and NSP-Wisconsin does not expect implementation of the new disclosure guidance to have a material impact to its consolidated financial statements. Income Taxes — In December 2023, the FASB issued ASU 2023-09 – Income Taxes (Topic 740) – Improvements to Income Tax Disclosures , with new disclosure requirements including presentation of prescribed line items in the effective tax rate reconciliation and disclosures regarding state and local tax payments. The ASU is effective for annual periods beginning after Dec. 15, 2024, and NSP-Wisconsin does not expect implementation of the new disclosure guidance to have a material impact to its consolidated financial statements. Climate-Related Disclosures — In March 2024, the SEC issued Final Rule 33-11275 – The Enhancement and Standardization of Climate-Related Disclosures for Investors. This rule requires registrants to provide standardized disclosures in Form 10-K related to climate-related risks, Scope 1 and 2 greenhouse gas emissions, as well as to include in a footnote to the consolidated financial statements the financial impact of severe weather events and other natural conditions. The rule requires implementation in phases between 2025 and 2033. In April 2024, the SEC announced that it would voluntarily stay its final climate disclosure rules pending judicial review. NSP-Wisconsin does not expect implementation of the new guidance to have a material impact on the consolidated financial statements.

Selected Balance Sheet Data

Selected Balance Sheet Data	9 Months Ended
	Sep. 30, 2024
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Accounts receivable, net Accounts receivable $ 76 $ 98 Less allowance for bad debts (7) (9) Accounts receivable, net $ 69 $ 89 (Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Inventories Materials and supplies $ 13 $ 11 Fuel 9 10 Natural gas 6 8 Total inventories $ 28 $ 29 (Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Property, plant and equipment, net Electric plant $ 4,043 $ 3,845 Natural gas plant 532 502 Common and other property 296 278 Construction work in progress 382 252 Total property, plant and equipment 5,253 4,877 Less accumulated depreciation (1,700) (1,640) Property, plant and equipment, net $ 3,553 $ 3,237

Borrowings and Other Financing

Borrowings and Other Financing Instruments	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	Short-Term Borrowings NSP-Wisconsin meets its short-term liquidity requirements primarily through the issuance of commercial paper and borrowings under its credit facility and the money pool. Money Pool — Xcel Energy Inc. and its utility subsidiaries have established a money pool arrangement that allows for short-term investments in and borrowings between the utility subsidiaries. Xcel Energy Inc. may make investments in the utility subsidiaries at market-based interest rates; however, the money pool arrangement does not allow the utility subsidiaries to make investments in Xcel Energy Inc. Money pool borrowings: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2024 Year Ended Dec. 31, 2023 Borrowing limit $ 150 $ 150 Amount outstanding at period end — — Average amount outstanding — 6 Maximum amount outstanding — 43 Weighted average interest rate, computed on a daily basis N/A 4.98% Weighted average interest rate at period end N/A N/A Commercial Paper — Commercial paper outstanding: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2024 Year Ended Dec. 31, 2023 Borrowing limit $ 150 $ 150 Amount outstanding at period end — 60 Average amount outstanding — 15 Maximum amount outstanding N/A 93 Weighted average interest rate, computed on a daily basis N/A 4.85% Weighted average interest rate at period end N/A 5.50 Letters of Credit — NSP-Wisconsin uses letters of credit, generally with terms of one year, to provide financial guarantees for certain obligations. At both Sept. 30, 2024 and Dec. 31, 2023, there we re immaterial l etters of credit outstanding under the credit facility. Revolving Credit Facility — In order to issue its commercial paper, NSP-Wisconsin must have a revolving credit facility equal to or greater than the commercial paper borrowing limit and cannot issue commercial paper exceeding available capacity under this credit facility. The credit facility provides short-term financing in the form of notes payable to banks, letters of credit and back-up support for commercial paper borrowings. NSP-Wisconsin has the right to request an extension of the revolving credit facility termination date for an additional one-year period. All extension requests are subject to majority bank group approval. As of Sept. 30, 2024, NSP-Wisconsin had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 150 $ — $ 150 (a) Expires in September 2027. (b) Includes outstanding commercial paper. All credit facility ban k borrowings, outstanding letters of credit and outstanding commercial paper reduce the available capacity under the credit facility. NSP-Wisconsin had no direct advances on the credit facility outstanding at Sept. 30, 2024 and Dec. 31, 2023. Other Short-Term Borrowings — Clearwater Investments, Inc., a NSP-Wisconsin subsidiary, had an immaterial note payable to Xcel Energy Inc. as of Sept. 30, 2024 and Dec. 31, 2023. Long-Term Borrowings During the nine months ended September 30, 2024, NSP-Wisconsin issued $400 million of 5.65% First Mortgage Bonds due June 15, 2054.

Revenues

Revenues	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenues	Revenue is classified by the type of goods/services rendered and market/customer type. NSP-Wisconsin’s operating revenues consisted of the following: Three Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 81 $ 8 $ 89 C&I 138 6 144 Other 2 — 2 Total retail 221 14 235 Interchange and other 54 2 56 Total revenue from contracts with customers 275 16 291 Alternative revenue and other 3 1 4 Total revenues $ 278 $ 17 $ 295 Three Months Ended (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 79 $ 8 $ — $ 87 C&I 136 5 — 141 Other 2 — 1 3 Total retail 217 13 1 231 Interchange and other 43 1 — 44 Total revenue from contracts with customers 260 14 1 275 Alternative revenue and other 3 1 — 4 Total revenues $ 263 $ 15 $ 1 $ 279 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 224 $ 50 $ 274 C&I 375 36 411 Other 5 — 5 Total retail 604 86 690 Interchange and other 167 4 171 Total revenue from contracts with customers 771 90 861 Alternative revenue and other 9 2 11 Total revenues $ 780 $ 92 $ 872 Nine Months Ended (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 229 $ 62 $ — $ 291 C&I 378 48 — 426 Other 6 — 1 7 Total retail 613 110 1 724 Interchange and other 131 2 — 133 Total revenue from contracts with customers 744 112 1 857 Alternative revenue and other 9 4 — 13 Total revenues $ 753 $ 116 $ 1 $ 870

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes Reconciliation between the statutory rate and effective tax rate: Nine Months Ended Sept. 30 2024 2023 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Decreases: Plant regulatory differences (a) (4.5) (3.4) Other, net (0.2) (1.1) Effective income tax rate 22.5 % 22.7 % (a)

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	7. Fair Value of Financial Assets and Liabilities Fair Value Measurements Accounting guidance for fair value measurements and disclosures provides a hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value. • Level 1 — Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. The types of assets and liabilities included in Level 1 are actively traded instruments with observable actual trading prices. • Level 2 — Pricing inputs are other than actual trading prices in active markets, but are either directly or indirectly observable as of the reporting date. The types of assets and liabilities included in Level 2 are typically either comparable to actively traded securities or contracts or priced with models using highly observable inputs. • Level 3 — Significant inputs to pricing have little or no observability as of the reporting date. The types of assets and liabilities included in Level 3 include those valued with models requiring significant judgment or estimation. Specific valuation methods include: Commodity Derivatives — Methods used to measure the fair value of commodity derivative forwards and options utilize forward prices and volatilities, as well as pricing adjustments for specific delivery locations, and are generally assigned a Level 2 classification. When contracts relate to inactive delivery locations or extend to periods beyond those readily observable on active exchanges, the significance of the use of less observable inputs on a valuation is evaluated, and may result in Level 3 classification. Derivative Activities and Fair Value Measurements NSP-Wisconsin enters into derivative instruments, including forward contracts, futures, swaps and options, to manage risk in connection with changes in utility commodity prices. As of Sept. 30, 2024, the gross notional amount of options for NSP-Wisconsin was immaterial. Commodity Derivatives — NSP-Wisconsin enters into derivative instruments to manage variability of future cash flows from changes in commodity prices in its electric and natural gas operations. This could include the purchase or sale of natural gas to generate electric energy and natural gas for resale. As of Sept. 30, 2024, NSP-Wisconsin had no commodity contracts designated as cash flow hedges. Consideration of Credit Risk and Concentrations — NSP-Wisconsin continuously monitors the creditworthiness of counterparties to its interest rate derivatives and commodity derivative contracts prior to settlement, and assesses each counterparty’s ability to perform on the transactions set forth in the contracts. Impact of credit risk was immaterial to the fair value of unsettled commodity derivatives presented on the consolidated balance sheets. Recurring Derivative Fair Value Measurements — Changes in the fair value of natural gas commodity derivatives resulted in immaterial net gains for the three and nine months ended Sept. 30, 2024 and 2023, which were recognized as regulatory assets and liabilities. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms. During the three and nine months ended Sept. 30, 2024 and 2023, an immaterial amount of pre-tax losses were recognized during the period related to option premium amortization. NSP-Wisconsin had immaterial outstanding derivative assets or liabilities measured at fair value as of Sept. 30, 2024 and Dec. 31, 2023. Fair Value of Long-Term Debt As of Sept. 30, 2024, other financial instruments for which the carrying amount did not equal fair value: Sept. 30, 2024 Dec. 31, 2023 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 1,405 $ 1,373 $ 1,211 $ 1,117 Fair value of NSP-Wisconsin’s long-term debt is estimated based on recent trades and observable spreads from benchmark interest rates for similar securities. Fair value estimates are based on information available to management as of Sept. 30, 2024 and Dec. 31, 2023, and given the observability of the inputs, fair values presented for long-term debt were assigned as Level 2.

Benefit Plans and Other Postret

Benefit Plans and Other Postretirement Benefits	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost Three Months Ended Sept. 30 2024 2023 (Millions of Dollars) Pension Benefits Service cost $ 1 $ 1 Interest cost (a) 1 2 Expected return on plan assets (a) (2) (2) Net periodic benefit cost — 1 Net benefit cost recognized for financial reporting $ — $ 1 Nine Months Ended Sept. 30 2024 2023 (Millions of Dollars) Pension Benefits Service cost $ 3 $ 3 Interest cost (a) 4 5 Expected return on plan assets (a) (6) (6) Amortization of net loss (a) 1 1 Settlement charge (b) 5 — Net periodic benefit cost 7 3 Effects of regulation (2) — Net benefit cost recognized for financial reporting $ 5 $ 3 (a) The components of net periodic cost other than the service cost component are included in the line item “Other income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset. (b) A settlement charge is required when the amount of lump-sum distributions during the year is greater than the sum of the service and interest cost components of the annual net periodic pension cost. In the nine months ended Sept. 30, 2024, as a result of lump-sum distributions during the 2024 plan year, NSP-Wisconsin recorded a pension settlement charge of $5 million, of which $1 million was recognized in the consolidated statement of income after considering the effects of regulation for the nine months ended Sept. 30, 2024.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Legal NSP-Wisconsin is involved in various litigation matters in the ordinary course of business. The assessment of whether a loss is probable or is a reasonable possibility, and whether the loss or a range of loss is estimable, often involves a series of complex judgments about future events. Management maintains accruals for losses probable of being incurred and subject to reasonable estimation. Management is sometimes unable to estimate an amount or range of a reasonably possible loss in certain situations, including but not limited to when (1) the damages sought are indeterminate, (2) the proceedings are in the early stages, or (3) the matters involve novel or unsettled legal theories. In such cases, there is considerable uncertainty regarding the timing or ultimate resolution, including a possible eventual loss. For current proceedings not specifically reported herein, management does not anticipate that the ultimate liabilities, if any, would have a material effect on NSP-Wisconsin’s consolidated financial statements. Legal fees are generally expensed as incurred. Gas Trading Litigation — e prime is a wholly owned subsidiary of Xcel Energy. e prime was in the business of natural gas trading and marketing but has not engaged in natural gas trading or marketing activities since 2003. Multiple lawsuits involving multiple plaintiffs seeking monetary damages were commenced against e prime and its affiliates, including Xcel Energy, between 2003 and 2009 alleging fraud and anticompetitive activities in conspiring to restrain the trade of natural gas and manipulate natural gas prices. Cases were all consolidated in the U.S. District Court in Nevada. One case remains active which includes a multi-district litigation matter consisting of a Wisconsin purported class (Arandell Corp.). The Court issued a ruling in June 2022 granting plaintiffs’ class certification. In April 2023, the Seventh Circuit Court of Appeals heard the defendants’ appeal challenging whether the district court properly assessed class certification. A decision relating to class certification is expected imminently. Xcel Energy considers the reasonably possible loss associated with this litigation to be immaterial. Rate Matters NSP-Wisconsin is involved in various regulatory proceedings arising in the ordinary course of business. Until resolution, typically in the form of a rate order, uncertainties may exist regarding the ultimate rate treatment for certain activities and transactions. Amounts have been recognized for probable and reasonably estimable losses that may result. Unless otherwise disclosed, any reasonably possible range of loss in excess of any recognized amount is not expected to have a material effect on the financial statements. Environmental New and changing federal and state environmental mandates can create financial obligations for NSP-Wisconsin, which are normally recovered through the regulated rate process. Site Remediation Various federal and state environmental laws impose liability where hazardous substances or other regulated materials have been released to the environment. NSP-Wisconsin may sometimes pay all or a portion of the cost to remediate sites where past activities of their predecessors or other parties have caused environmental contamination. Environmental contingencies could arise from various situations, including sites of former MGPs; and third-party sites, such as landfills, for which NSP-Wisconsin is alleged to have sent wastes to that site. MGP, Landfill and Disposal Sites NSP-Wisconsin is investigating, remediating or performing post-closure actions at one MGP, landfill or other disposal sites across its service territories. NSP-Wisconsin has recognized approximately $12 million of costs/liabilities for resolution of these issues; however, the final outcomes and timing are unknown. In addition, there may be regulatory recovery, insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of costs incurred. Water and Waste Coal Ash Regulation — NSP-Wisconsin is subject to the CCR Rule, which imposes requirements for handling, storage, treatment and disposal of coal ash and other solid waste. In May 2024, final amendments to the CCR Rule were published, widening its scope to include legacy CCR surface impoundments at inactive facilities and previously exempt areas where CCR was placed directly on land at CCR-regulated facilities, including areas of beneficial use. As a requirement of the CCR Rule, utilities must complete facility evaluations and groundwater sampling around their subject landfills, surface impoundments and certain other areas where coal ash was placed on land. If certain impacts to groundwater are detected, utilities may be required to perform additional groundwater investigations and/or perform corrective actions, typically beginning with an Assessment of Corrective Measures. NSP-Wisconsin expects to incur nominal expenses for investigations through 2028 to perform required reporting and assess whether corrective actions are necessary. Asset retirement obligations have been recorded for each of these activities, and amounts are expected to be recoverable through regulatory mechanisms. NSP-Wisconsin continues to evaluate the 2024 updates to the CCR rule, the interpretations of those updates and how they will apply to specific sites. Assessment of the recent updates to the CCR Rule and corresponding site investigation activities may result in updates to estimated costs as well as identification of additional required corrective actions. Clean Water Act Section 316(b) — The Federal Clean Water Act requires the EPA to regulate cooling water intake structures to assure they reflect the best technology available for minimizing impingement and entrainment of aquatic species. NSP-Wisconsin estimates capital expenditures of approximately $5 million may be required to comply with the requirements. NSP-Wisconsin believes two plants could be required to make improvements to reduce impingement and entrainment. NSP-Wisconsin anticipates these costs will be recoverable through regulatory mechanisms. Air Clean Air Act NOx Allowance Allocations — In June 2023, the EPA published final regulations for ozone under the “Good Neighbor” provisions of the Clean Air Act. The final rule applies to generation facilities in Wisconsin, as well as other states outside of our service territory. The rule establishes an allowance trading program for NOx that will impact NSP-Wisconsin fossil fuel-fired electric generating facilities. Subject facilities will have to secure additional allowances, install NOx controls and/or develop a strategy of operations that utilizes the existing allowance allocations. While the financial impacts of the final rule are uncertain and dependent on market forces and anticipated generation, NSP-Wisconsin anticipates the annual costs could be significant, but would be recoverable through regulatory mechanisms In June 2024, the U.S. Supreme Court issued an order granting a stay of the final rule. In response, the EPA has communicated intent to issue an administrative stay of the rule nationwide. Depending on the outcomes of the underlying legal challenges, the regulation may become applicable in the future.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Segment Information	NSP-Wisconsin evaluates performance based on profit or loss generated from the product or service provided. These segments are managed separately because the revenue streams are dependent upon regulated rate recovery, which is separately determined for each segment. NSP-Wisconsin has the following reportable segments: • Regulated Electric — The regulated electric utility segment generates electricity, which is transmitted and distributed in Wisconsin and Michigan. • Regulated Natural Gas — The regulated natural gas utility segment purchases, transports, stores and distributes natural gas in portions of Wisconsin and Michigan. Asset and capital expenditure information is not provided for NSP-Wisconsin's reportable segments. As an integrated electric and natural gas utility, NSP-Wisconsin operates significant assets that are not dedicated to a specific business segment. Reporting assets and capital expenditures by business segment would require arbitrary and potentially misleading allocations, which may not necessarily reflect the assets that would be required for the operation of the business segments on a stand-alone basis. Certain costs, such as common depreciation, common O&M expenses and interest expense are allocated based on cost causation allocators across each segment. In addition, a general allocator is used for certain general and administrative expenses, including office supplies, rent, property insurance and general advertising. NSP-Wisconsin's segment information: Three Months Ended Sept. 30 (Millions of Dollars) 2024 2023 Regulated Electric Total revenues (a) $ 278 $ 263 Net income 43 32 Regulated Natural Gas Total revenues $ 17 $ 15 Net loss (4) (3) All Other Total revenues $ — $ 1 Net income $ 2 $ 2 Consolidated Total Total revenues (a) $ 295 $ 279 Net income 41 31 (a) Total revenues include $53 million and $50 million of affiliate electric revenue for the three months ended Sept. 30, 2024 and 2023, respectively. Nine Months Ended Sept. 30 (Millions of Dollars) 2024 2023 Regulated Electric Total revenues (a) $ 780 $ 753 Net income 99 95 Regulated Natural Gas Operating revenues $ 92 $ 116 Intersegment revenue — 1 Total revenues $ 92 $ 117 Net income 4 5 All Other Total revenues $ — $ 1 Net income $ 4 $ 2 Consolidated Total Total revenues (a) $ 872 $ 871 Reconciling eliminations — (1) Total operating revenues $ 872 $ 870 Net income 107 102 (a) Total revenues include $160 million and $151 million of affiliate electric revenue for the nine months ended Sept. 30, 2024 and 2023, respectively.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net income	$ 41	$ 31	$ 107	$ 102

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	9 Months Ended
	Sep. 30, 2024
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Accounts receivable, net Accounts receivable $ 76 $ 98 Less allowance for bad debts (7) (9) Accounts receivable, net $ 69 $ 89
Inventories	(Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Inventories Materials and supplies $ 13 $ 11 Fuel 9 10 Natural gas 6 8 Total inventories $ 28 $ 29
Property, Plant and Equipment, Net	(Millions of dollars) Sept. 30, 2024 Dec. 31, 2023 Property, plant and equipment, net Electric plant $ 4,043 $ 3,845 Natural gas plant 532 502 Common and other property 296 278 Construction work in progress 382 252 Total property, plant and equipment 5,253 4,877 Less accumulated depreciation (1,700) (1,640) Property, plant and equipment, net $ 3,553 $ 3,237

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	9 Months Ended
	Sep. 30, 2024
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	As of Sept. 30, 2024, NSP-Wisconsin had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 150 $ — $ 150 (a) Expires in September 2027. (b) Includes outstanding commercial paper.
Money Pool
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Money pool borrowings: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2024 Year Ended Dec. 31, 2023 Borrowing limit $ 150 $ 150 Amount outstanding at period end — — Average amount outstanding — 6 Maximum amount outstanding — 43 Weighted average interest rate, computed on a daily basis N/A 4.98% Weighted average interest rate at period end N/A N/A
Commercial Paper
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Commercial paper outstanding: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2024 Year Ended Dec. 31, 2023 Borrowing limit $ 150 $ 150 Amount outstanding at period end — 60 Average amount outstanding — 15 Maximum amount outstanding N/A 93 Weighted average interest rate, computed on a daily basis N/A 4.85% Weighted average interest rate at period end N/A 5.50

Revenues (Tables)

Revenues (Tables)	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	Revenue is classified by the type of goods/services rendered and market/customer type. NSP-Wisconsin’s operating revenues consisted of the following: Three Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 81 $ 8 $ 89 C&I 138 6 144 Other 2 — 2 Total retail 221 14 235 Interchange and other 54 2 56 Total revenue from contracts with customers 275 16 291 Alternative revenue and other 3 1 4 Total revenues $ 278 $ 17 $ 295 Three Months Ended (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 79 $ 8 $ — $ 87 C&I 136 5 — 141 Other 2 — 1 3 Total retail 217 13 1 231 Interchange and other 43 1 — 44 Total revenue from contracts with customers 260 14 1 275 Alternative revenue and other 3 1 — 4 Total revenues $ 263 $ 15 $ 1 $ 279 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 224 $ 50 $ 274 C&I 375 36 411 Other 5 — 5 Total retail 604 86 690 Interchange and other 167 4 171 Total revenue from contracts with customers 771 90 861 Alternative revenue and other 9 2 11 Total revenues $ 780 $ 92 $ 872 Nine Months Ended (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 229 $ 62 $ — $ 291 C&I 378 48 — 426 Other 6 — 1 7 Total retail 613 110 1 724 Interchange and other 131 2 — 133 Total revenue from contracts with customers 744 112 1 857 Alternative revenue and other 9 4 — 13 Total revenues $ 753 $ 116 $ 1 $ 870

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Reconciliation between the statutory rate and effective tax rate: Nine Months Ended Sept. 30 2024 2023 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Decreases: Plant regulatory differences (a) (4.5) (3.4) Other, net (0.2) (1.1) Effective income tax rate 22.5 % 22.7 % (a)

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Carrying Amount and Fair Value of Long-term Debt	Sept. 30, 2024 Dec. 31, 2023 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 1,405 $ 1,373 $ 1,211 $ 1,117

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost Three Months Ended Sept. 30 2024 2023 (Millions of Dollars) Pension Benefits Service cost $ 1 $ 1 Interest cost (a) 1 2 Expected return on plan assets (a) (2) (2) Net periodic benefit cost — 1 Net benefit cost recognized for financial reporting $ — $ 1 Nine Months Ended Sept. 30 2024 2023 (Millions of Dollars) Pension Benefits Service cost $ 3 $ 3 Interest cost (a) 4 5 Expected return on plan assets (a) (6) (6) Amortization of net loss (a) 1 1 Settlement charge (b) 5 — Net periodic benefit cost 7 3 Effects of regulation (2) — Net benefit cost recognized for financial reporting $ 5 $ 3 (a) The components of net periodic cost other than the service cost component are included in the line item “Other income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset. (b) A settlement charge is required when the amount of lump-sum distributions during the year is greater than the sum of the service and interest cost components of the annual net periodic pension cost. In the nine months ended Sept. 30, 2024, as a result of lump-sum distributions during the 2024 plan year, NSP-Wisconsin recorded a pension settlement charge of $5 million, of which $1 million was recognized in the consolidated statement of income after considering the effects of regulation for the nine months ended Sept. 30, 2024. In January 2024, contributions totaling $100 million were made across Xcel Energy’s pension plans, of which $7 million was attributable to NSP-Wisconsin. Xcel Energy does not expect additional pension contributions during 2024.

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	NSP-Wisconsin's segment information: Three Months Ended Sept. 30 (Millions of Dollars) 2024 2023 Regulated Electric Total revenues (a) $ 278 $ 263 Net income 43 32 Regulated Natural Gas Total revenues $ 17 $ 15 Net loss (4) (3) All Other Total revenues $ — $ 1 Net income $ 2 $ 2 Consolidated Total Total revenues (a) $ 295 $ 279 Net income 41 31 (a) Total revenues include $53 million and $50 million of affiliate electric revenue for the three months ended Sept. 30, 2024 and 2023, respectively. Nine Months Ended Sept. 30 (Millions of Dollars) 2024 2023 Regulated Electric Total revenues (a) $ 780 $ 753 Net income 99 95 Regulated Natural Gas Operating revenues $ 92 $ 116 Intersegment revenue — 1 Total revenues $ 92 $ 117 Net income 4 5 All Other Total revenues $ — $ 1 Net income $ 4 $ 2 Consolidated Total Total revenues (a) $ 872 $ 871 Reconciling eliminations — (1) Total operating revenues $ 872 $ 870 Net income 107 102 (a) Total revenues include $160 million and $151 million of affiliate electric revenue for the nine months ended Sept. 30, 2024 and 2023, respectively.

Selected Balance Sheet Data - A

Selected Balance Sheet Data - Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Accounts Receivable, Net
Accounts receivable	$ 76	$ 98
Less allowance for bad debts	(7)	(9)
Accounts receivable, net	$ 69	$ 89

Selected Balance Sheet Data - I

Selected Balance Sheet Data - Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Inventory [Line Items]
Total Inventories	$ 28	$ 29
Materials and supplies
Inventory [Line Items]
Inventories	13	11
Fuel
Inventory [Line Items]
Inventories	9	10
Natural gas
Inventory [Line Items]
Inventories	$ 6	$ 8

Selected Balance Sheet Data - P

Selected Balance Sheet Data - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Public Utility, Property, Plant and Equipment [Line Items]
Common and other property	$ 296	$ 278
Construction work in progress	382	252
Total property, plant and equipment	5,253	4,877
Less accumulated depreciation	(1,700)	(1,640)
Property, plant and equipment, net	3,553	3,237
Electricity Generation Plant, Non-Nuclear
Public Utility, Property, Plant and Equipment [Line Items]
Plant	4,043	3,845
Natural Gas Processing Plant
Public Utility, Property, Plant and Equipment [Line Items]
Plant	$ 532	$ 502

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments, Commercial Paper (Details) - USD ($)		3 Months Ended	12 Months Ended
		Sep. 30, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Amount outstanding at period end		$ 0	$ 60,000,000
Credit Facility
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]	150,000,000
Long-term Line of Credit		0	0
Commercial Paper
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150,000,000	150,000,000
Amount outstanding at period end		0	60,000,000
Average amount outstanding		0	15,000,000
Maximum amount outstanding			$ 93,000,000
Weighted average interest rate, computed on a daily basis			4.85%
Weighted average interest rate at period end			5.50%
Money Pool
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150,000,000	$ 150,000,000
Amount outstanding at period end		0	0
Average amount outstanding		0	6,000,000
Maximum amount outstanding		0	$ 43,000,000
Weighted average interest rate, computed on a daily basis			4.98%
Series Due June 15, 2054 | Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage		5.65%
[1] Expires in September 2027.

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments, Letters of Credit (Details) - USD ($)	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Period	1 year
Amount outstanding at period end	$ 0	$ 60,000,000
Credit Facility
Line of Credit Facility [Line Items]
Long-term Line of Credit	$ 0	$ 0

Borrowings and Other Financin_5

Borrowings and Other Financing Instruments, Credit Facility (Details) - USD ($)		Sep. 30, 2024	Dec. 31, 2023
Payable to Affiliates
Line of Credit Facility [Line Items]
Notes Payable, Current		$ 0	$ 0
Credit Facility
Line of Credit Facility [Line Items]
Credit Facility	[1]	150,000,000
Outstanding	[2]	0
Available		150,000,000
Direct advances on the credit facility outstanding		$ 0	$ 0
[1] Expires in September 2027. Includes outstanding commercial paper.

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 295	$ 279	$ 872	$ 870
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	278	263	780	753
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	17	15	92	116
All Other | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues		1		1
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	235	231	690	724
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	89	87	274	291
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	144	141	411	426
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	3	5	7
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	221	217	604	613
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	79	224	229
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	138	136	375	378
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	5	6
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	13	86	110
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8	8	50	62
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	5	36	48
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Retail | All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1		1
Retail | All Other | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0		0
Retail | All Other | C&I
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0		0
Retail | All Other | Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1		1
Interchange
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	56	44	171	133
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	54	43	167	131
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	1	4	2
Interchange | All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0		0
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	291	275	861	857
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	275	260	771	744
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16	14	90	112
Total revenue from contracts with customers | All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1		1
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	4	4	11	13
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	3	9	9
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 1	1	$ 2	4
Alternative revenue and other | All Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other		$ 0		$ 0

Income Taxes (Details)

Income Taxes (Details)		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21%	21%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		6.20%	6.20%
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[1]	(4.50%)	(3.40%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		(0.20%)	(1.10%)
Effective Income Tax Rate Reconciliation, Percent		22.50%	22.70%
[1]Plant regulatory differences primarily relate to the credit of excess deferred taxes to customers. Income tax benefits associated with the credit are offset by corresponding revenue reductions.

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Commodity Derivatives (Details) $ in Millions	Sep. 30, 2024 USD ($)
cash flow hedge commodity
Derivative [Line Items]
Commodity contracts designated as cash flow hedges	$ 0

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	$ 1,405	$ 1,211
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 1,373	$ 1,117

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
		Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Components of Net Periodic Benefit Cost [Abstract]
Operating and maintenance expenses			$ 55	$ 58	$ 170	$ 173
Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			1	1	3	3
Interest cost (a)	[1]		1	2	4	5
Expected return on plan assets (a)	[1]		(2)	(2)	(6)	(6)
Amortization of net loss (a)	[1]				1	1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]				5	0
Net periodic benefit cost			0	1	7	3
Effects of regulation					(2)	0
Net benefit cost recognized for financial reporting			$ 0	$ 1	5	$ 3
Contributions to pension plans		$ 7
Operating and maintenance expenses					$ 1
Pension Plan [Member] | Parent Company [Member]
Components of Net Periodic Benefit Cost [Abstract]
Contributions to pension plans		$ 100
[1] The components of net periodic cost other than the service cost component are included in the line item “Other income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset. A settlement charge is required when the amount of lump-sum distributions during the year is greater than the sum of the service and interest cost components of the annual net periodic pension cost. In the nine months ended Sept. 30, 2024, as a result of lump-sum distributions during the 2024 plan year, NSP-Wisconsin recorded a pension settlement charge of $5 million, of which $1 million was recognized in the consolidated statement of income after considering the effects of regulation for the nine months ended Sept. 30, 2024.

Commitments and Contingencies G

Commitments and Contingencies Gas Trading Litigation (Details)	Sep. 30, 2024
Gas Trading Litigation
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number	1

Commitments and Contingencies (

Commitments and Contingencies (Details) - Enviromental Requirements $ in Millions	Sep. 30, 2024 USD ($)
Loss Contingencies [Line Items]
Cost of identified MGP, landfill, or disposal sites under current investigation and/or remediation	$ 12
Liability for estimated cost to comply with regulation	$ 5
Plants required for improvements	2
Legacy CCR Investigation and Remediation Costs	$ 0
Other MGP, Landfill, or Disposal Sites [Domain]
Loss Contingencies [Line Items]
Number of identified MGP sites under current investigation and/or remediation	1

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2024		Sep. 30, 2023		Sep. 30, 2024		Sep. 30, 2023
Segment Reporting Information [Line Items]
Net income	$ 41		$ 31		$ 107		$ 102
Natural gas	17		15		92		116
Other	0		1		0		1
Regulated and Unregulated Operating Revenue	295		279		872		870
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	295	[1]	279	[1]	872	[2]	871	[2]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue					0		(1)
Regulated Electric
Segment Reporting Information [Line Items]
Net income	43		32		99		95
Regulated Electric | Total revenues
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	278	[1]	263	[1]	780	[2]	753	[2]
Regulated Natural Gas
Segment Reporting Information [Line Items]
Net income	(4)		(3)		4		5
Revenues Including Intersegment Revenues	17		15		92		117
Regulated Natural Gas | Total revenues
Segment Reporting Information [Line Items]
Natural gas					92		116
Regulated Natural Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Natural gas					0		1
All Other
Segment Reporting Information [Line Items]
Net income	2		2		4		2
All Other | Total revenues
Segment Reporting Information [Line Items]
Other	$ 0		$ 1		$ 0		$ 1
[1] Total revenues include $53 million and $50 million of affiliate electric revenue for the three months ended Sept. 30, 2024 and 2023, respectively. Total revenues include $160 million and $151 million of affiliate electric revenue for the nine months ended Sept. 30, 2024 and 2023, respectively.