Northern States Power 10-Q 28 Oct 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Oct. 28, 2021
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	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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	737-2625
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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating revenues
Electric, non-affiliates	$ 203	$ 195	$ 559	$ 524
Electric, affiliates	49	41	141	123
Natural gas	22	15	110	79
Total operating revenues	274	251	810	726
Operating expenses
Electric fuel and purchased power, non-affiliates	5	3	15	10
Purchased power, affiliates	106	100	312	285
Cost of natural sold and transported	13	6	64	33
Operating and maintenance expenses	47	47	146	141
Conservation program expenses	4	3	10	10
Depreciation and amortization	37	39	110	116
Taxes (other than income taxes)	7	7	22	21
Total operating expenses	219	205	679	616
Operating income	55	46	131	110
Other expense, net	(1)	(2)	(1)	(6)
Allowance for funds used during construction — equity	2	2	4	4
Interest charges and financing costs
Interest charges	10	11	31	30
Allowance for funds used during construction — debt	0	(1)	(1)	(2)
Total interest charges and financing costs	10	10	30	28
Income before income taxes	46	36	104	80
Income tax expense (benefit)	10	(4)	22	(5)
Net income	$ 36	$ 40	$ 82	$ 85

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net income	$ 82	$ 85
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	110	117
Deferred income taxes	10	(29)
Allowance for equity funds used during construction	(4)	(4)
Provision for bad debts	2	4
Changes in operating assets and liabilities:
Accounts receivable	11	(1)
Accrued unbilled revenues	8	12
Inventories	(9)	(5)
Other current assets	5	4
Accounts payable	(2)	(4)
Net regulatory assets and liabilities	(50)	1
Other current liabilities	(6)	3
Pension and other employee benefit obligations	(7)	(7)
Other, net	2	0
Net cash provided by operating activities	152	176
Investing activities
Capital/construction expenditures	(182)	(185)
Investments in utility money pool arrangement	(71)	0
Repayments from utility money pool arrangement	71	0
Net cash used in investing activities	(182)	(185)
Financing activities
Repayments of short-term borrowings, net	(19)	(65)
Borrowings under utility money pool arrangement	236	0
Repayments under utility money pool arrangement	(236)	0
Proceeds from long-term debt	99	98
Capital contributions from parent	42	38
Dividends paid to parent	(82)	(52)
Net cash provided by financing activities	40	19
Net change in cash, cash equivalents and restricted cash	10	10
Cash, cash equivalents and restricted cash at beginning of period	2	1
Cash, cash equivalents and restricted cash at end of period	12	11
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(29)	(28)
Cash paid for income taxes, net	(17)	(19)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	23	16
Inventory transfers to property, plant and equipment	2	4
Allowance for equity funds used during construction	$ 4	$ 4

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 12	$ 2
Accounts receivable, net	60	70
Accrued unbilled revenues	45	53
Other Receivables	3	1
Inventories	23	15
Regulatory assets	43	19
Prepaid taxes	18	24
Prepayments and other	8	7
Total current assets	212	191
Property, Plant and Equipment, Net [Abstract]
Property, plant and equipment, net	2,590	2,484
Other assets
Regulatory assets	219	215
Other Investments	3	3
Other	1	1
Total other assets	223	219
Total assets	3,025	2,894
Current liabilities
Current portion of long-term debt	19	19
Short-term debt	0	19
Accounts payable	46	41
Accounts payable to affiliates	21	15
Dividends payable to parent	20	19
Regulatory liabilities	8	31
Taxes accrued	4	12
Environmental liabilities	4	4
Accrued interest	10	10
Other	16	15
Total current liabilities	148	185
Deferred credits and other liabilities
Deferred income taxes	324	307
Regulatory liabilities	369	350
Environmental liabilities	15	16
Customer advances	23	20
Pension and employee benefit obligations	23	28
Other	33	33
Total deferred credits and other liabilities	787	754
Commitments and contingencies
Capitalization
Long-term debt	987	887
Common Stock - 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at Sept. 30, 2020 and Dec. 31, 2019, 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	$ 641	$ 605
Retained earnings	369	370
Total common stockholder's equity	1,103	1,068
Total liabilities and equity	$ 3,025	$ 2,894

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, 2019		933,000
Beginning Balance at Dec. 31, 2019	$ 966	$ 93	$ 537	$ 336
Increase (Decrease) in Stockholder's Equity
Net income	85
Common dividends declared to parent	(55)			(55)
Contribution of capital by parent	41		41
Balance (in shares) at Sep. 30, 2020		933,000
Ending Balance at Sep. 30, 2020	1,037	$ 93	578	366
Balance (in shares) at Jun. 30, 2020		933,000
Beginning Balance at Jun. 30, 2020	1,015	$ 93	578	344
Increase (Decrease) in Stockholder's Equity
Net income	40			40
Common dividends declared to parent	(18)			(18)
Balance (in shares) at Sep. 30, 2020		933,000
Ending Balance at Sep. 30, 2020	$ 1,037	$ 93	578	366
Balance (in shares) at Dec. 31, 2020	933,000	933,000
Beginning Balance at Dec. 31, 2020	$ 1,068	$ 93	605	370
Increase (Decrease) in Stockholder's Equity
Net income	82
Common dividends declared to parent	(83)			(83)
Contribution of capital by parent	$ 36		36
Balance (in shares) at Sep. 30, 2021	933,000	933,000
Ending Balance at Sep. 30, 2021	$ 1,103	$ 93	641	369
Balance (in shares) at Jun. 30, 2021		933,000
Beginning Balance at Jun. 30, 2021	1,113	$ 93	638	382
Increase (Decrease) in Stockholder's Equity
Net income	36			36
Common dividends declared to parent	(49)			(49)
Contribution of capital by parent	$ 3		3
Balance (in shares) at Sep. 30, 2021	933,000	933,000
Ending Balance at Sep. 30, 2021	$ 1,103	$ 93	$ 641	$ 369

Management's Opinion

Management's Opinion	9 Months Ended
	Sep. 30, 2021
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, 2021 and Dec. 31, 2020; the results of NSP-Wisconsin's operations, including the components of net income, changes in stockholder's equity and comprehensive income for the three and nine months ended Sept. 30, 2021 and 2020; and NSP-Wisconsin's cash flows for the nine months ended Sept. 30, 2021 and 2020. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after Sept. 30, 2021 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, 2020 balance sheet information has been derived from the audited 2020 consolidated financial statements included in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2020. 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, 2020, filed with the SEC on Feb. 17, 2021. 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, 2021
Accounting Policies [Abstract]
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, 2020 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, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Pronouncements	Recently Adopted Credit Losses — In 2016, the FASB issued Financial Instruments - Credit Losses, Topic 326 (ASC Topic 326), which changes how entities account for losses on receivables and certain other assets. The guidance requires use of a current expected credit loss model, which may result in earlier recognition of credit losses than under previous accounting standards.

Selected Balance Sheet Data

Selected Balance Sheet Data	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Accounts receivable, net Accounts receivable $ 68 $ 78 Less allowance for bad debts (8) (8) Accounts receivable, net $ 60 $ 70 (Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Inventories Materials and supplies $ 7 $ 7 Fuel 6 4 Natural gas 10 4 Total inventories $ 23 $ 15 (Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Property, plant and equipment, net Electric plant $ 3,287 $ 3,197 Natural gas plant 411 391 Common and other property 226 221 Construction work in progress 122 71 Total property, plant and equipment 4,046 3,880 Less accumulated depreciation (1,456) (1,396) Property, plant and equipment, net $ 2,590 $ 2,484

Borrowings and Other Financing

Borrowings and Other Financing Instruments	9 Months Ended
	Sep. 30, 2021
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 for NSP-Wisconsin: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2021 Year Ended Dec. 31, 2020 Borrowing limit $ 150 $ — Amount outstanding at period end — — Average amount outstanding 11 — Maximum amount outstanding 60 — Weighted average interest rate, computed on a daily basis 0.05 % N/A Weighted average interest rate at period end N/A N/A Commercial Paper — Commercial paper outstanding for NSP-Wisconsin: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2021 Year Ended Dec. 31, 2020 Borrowing limit $ 150 $ 150 Amount outstanding at period end — 19 Average amount outstanding — 30 Maximum amount outstanding — 95 Weighted average interest rate, computed on a daily basis N/A 1.59 % Weighted average interest rate at period end N/A 0.17 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, 2021 and Dec. 31, 2020, there we re no 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 in place at least equal to the amount of its 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, 2021, 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 June 2024. (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, 2021 and Dec. 31, 2020. Other Short-Term Borrowings — As of Sept. 30, 2021 and Dec. 31, 2020, Clearwater Investments, Inc., a NSP-Wisconsin subsidiary, had no notes payable to Xcel Energy Inc.

Revenues

Revenues	9 Months Ended
	Sep. 30, 2021
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 $ 73 $ 8 $ 81 C&I 126 12 138 Other 2 — 2 Total retail 201 20 221 Interchange 48 — 48 Other — 2 2 Total revenue from contracts with customers 249 22 271 Alternative revenue and other 3 — 3 Total revenues $ 252 $ 22 $ 274 Three Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 71 $ 7 $ 78 C&I 119 6 125 Other 1 — 1 Total retail 191 13 204 Interchange 41 — 41 Other 1 1 2 Total revenue from contracts with customers 233 14 247 Alternative revenue and other 3 1 4 Total revenues $ 236 $ 15 $ 251 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 208 $ 54 $ 262 C&I 336 51 387 Other 7 — 7 Total retail 551 105 656 Interchange 140 — 140 Other — 4 4 Total revenue from contracts with customers 691 109 800 Alternative revenue and other 9 1 10 Total revenues $ 700 $ 110 $ 810 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 195 $ 43 $ 238 C&I 313 32 345 Other 5 — 5 Total retail 513 75 588 Interchange 123 — 123 Other 1 3 4 Total revenue from contracts with customers 637 78 715 Alternative revenue and other 10 1 11 Total revenues $ 647 $ 79 $ 726

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes Note 7 to the consolidated financial statements included in NSP-Wisconsin’s Annual Report on Form 10-K for the year ended Dec. 31, 2020 represents, in all material respects, the current status of other income tax matters except to the extent noted below, and are incorporated herein by reference. Difference between the statutory rate and ETR: Nine Months Ended Sept. 30 2021 2020 (a) Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Increases (decreases) in tax from: Plant regulatory differences (b) (3.9) (19.6) Amortization of excess nonplant deferred taxes — (12.8) Tax credits, net of NOL & tax credit allowances (1.0) (1.6) Other (net) (1.1) 0.5 Effective income tax rate 21.2 % (6.3) % (a) Prior periods have been restated to conform to current year presentation. (b) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions. Federal Audits — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s consolidated federal income tax returns expire as follows: Tax Years Expiration 2014 - 2016 December 2022 2018 September 2022 Additionally, the statute of limitations related to certain federal tax credit carryforwards will remain open until those credits are utilized in subsequent returns. Further, the statute of limitations related to a federal tax loss carryback claim filed in 2020 has been extended. Xcel Energy has recognized its best estimate of income tax expense that will result from a final resolution of this issue; however, the outcome and timing of a resolution is unknown . State Audits — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of Sept. 30, 2021, NSP-Wisconsin’s earliest open tax year subject to examination by state taxing authorities under applicable statutes of limitations is 2016. In March 2021, Wisconsin began an audit of tax years 2016 - 2019. No material adjustments have been proposed. Unrecognized Benefits — The unrecognized tax benefit balance includes permanent tax positions, which if recognized would affect the ETR. In addition, the unrecognized tax benefit balance includes temporary tax positions for which deductibility is highly certain, but for which there is uncertainty about the timing. A change in the timing of deductibility would not affect the ETR but would accelerate the payment to the taxing authority. Unrecognized tax benefits — permanent vs. temporary: (Millions of Dollars) Sept. 30, 2021 Dec. 31, 2020 Unrecognized tax benefit — Permanent tax positions $ 2 $ 1 Unrecognized tax benefit — Temporary tax positions 1 1 Total unrecognized tax benefit $ 3 $ 2 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) Sept. 30, 2021 Dec. 31, 2020 NOL and tax credit carryforwards $ (2) $ (2) As the Internal Revenue Service audits resume and state audit progresses, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $1 million in the next 12 months. Payables for interest related to unrecognized tax benefits were not material and no amounts were accrued for penalties related to unrecognized tax benefits as of Sept. 30, 2021 or Dec. 31, 2020.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 30, 2021
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 single definition of fair value and requires disclosures about assets and liabilities measured at fair value. A hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value is established by this guidance. • 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 highly liquid and actively traded instruments with quoted prices. • Level 2 — Pricing inputs are other than quoted 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 are those valued with models requiring significant management judgment or estimation. Specific valuation methods include: Cash equivalents — The fair values of cash equivalents are generally based on cost plus accrued interest; money market funds are measured using quoted net asset value. Interest rate derivatives — The fair values of interest rate derivatives are based on broker quotes that utilize current market interest rate forecasts. Commodity derivatives — The 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 contractual settlements relate to inactive delivery locations or extend to periods beyond those readily observable on active exchanges or quoted by brokers, the significance of the use of less observable inputs on a valuation is evaluated and may result in Level 3 classification. Derivative Instruments Fair Value Measurements NSP-Wisconsin enters into derivative instruments, including forward contracts, futures, swaps and options, for trading purposes and to manage risk in connection with changes in interest rates and utility commodity prices. Interest Rate Derivatives — NSP-Wisconsin may enter into various instruments that effectively fix the yield or price on a specified benchmark interest rate for an anticipated debt issuance for a specific period. These derivative instruments are generally designated as cash flow hedges for accounting purposes. As of Sept. 30, 2021 and Dec. 31, 2020, there were no interest rate derivatives designated as cash flow hedges. Commodity Derivatives — NSP-Wisconsin may enter into derivative instruments to manage variability of future cash flows from changes in commodity prices in its electric and natural gas operations, as well as for trading purposes. This could include the purchase or sale of natural gas to generate electric energy and natural gas for resale. Gross notional amounts of commodity options: (Amounts in Millions) (a)(b) Sept. 30, 2021 Dec. 31, 2020 Million British thermal units of natural gas 2 — (a) Amounts are not reflective of net positions in the underlying commodities. (b) Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise. 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. Impact of Derivative Activities on Income — Changes in the fair value of natural gas commodity derivatives resulted in $3 million in gains for the three and nine months ended Sept. 30, 2021 which were recognized as regulatory assets and liabilities. There were immaterial net gains for the three and nine months ended Sept. 30, 2020. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms. During the three months ended Sept. 30, 2021 and 2020, there were no settlement gains or losses on natural gas commodity derivatives. During the nine months ended Sept. 30, 2021 and 2020, there were $1 million of settlement losses, which were recognized subject to purchased natural gas cost recovery mechanisms, which result in reclassifications of derivative settlement gains and losses out of income to a regulatory asset or liability, as appropriate. NSP-Wisconsin had no derivative instruments designated as fair value hedges during the three and nine months ended Sept. 30, 2021 and 2020. Recurring Fair Value Measurements — NSP-Wisconsin's derivative assets measured at fair value on a recurring basis were as follows: Sept. 30, 2021 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 4 $ — $ 4 $ — $ 4 Dec. 31, 2020 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 1 $ — $ 1 $ — $ 1 (a) NSP-Wisconsin nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2021 and Dec. 31, 2020. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) Included in prepayments and other current assets balance of $8 million at Sept. 30, 2021 and $7 million at Dec. 31, 2020 on the consolidated balance sheets. Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: Sept. 30, 2021 Dec. 31, 2020 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 1,006 $ 1,173 $ 906 $ 1,124 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, 2021 and Dec. 31, 2020 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, 2021
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost Three Months Ended Sept. 30 2021 2020 (Millions of Dollars) Pension Benefits Service cost $ 1 $ 1 Interest cost (a) 1 1 Expected return on plan assets (a) (2) (2) Amortization of net loss (a) 2 1 Settlement charge (b) 3 — Net periodic benefit cost $ 5 $ 1 Effects of regulation (2) 2 Net benefit cost recognized for financial reporting $ 3 $ 3 Nine Months Ended Sept. 30 2021 2020 (Millions of Dollars) Pension Benefits Service cost $ 4 $ 3 Interest cost (a) 3 4 Expected return on plan assets (a) (6) (6) Amortization of net loss (a) 4 4 Settlement charge (b) 3 — Net periodic benefit cost $ 8 $ 5 Effects of regulation (2) 5 Net benefit cost recognized for financial reporting $ 6 $ 10 (a) The components of net periodic cost other than the service cost component are included in the line item “Other expense, 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 third quarter as a result of lump-sum distributions during the 2021 plan year, NSP-Wisconsin recorded a pension settlement charge of $3 million, the majority of which was not recognized in earnings due to the effects of regulation. In January 2021, contributions of $125 million were made across four of Xcel Energy’s pension plans, of which $5 million was attributable to NSP-Wisconsin. Xcel Energy does not expect additional pension contributions during 2021.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	The following includes commitments, contingencies and unresolved contingencies that are material to NSP-Wisconsin’s financial position. 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 remain active which include an MDL matter consisting of a Wisconsin purported class (Arandell Corp.). Breckenridge/Colorado — In February 2019, the MDL panel remanded Breckenridge back to the U.S. District Court in Colorado. Settlement of approximately $3 million was reached in February 2021. In July 2021, the settlement was approved. Arandell Corp. — The trial has been vacated and will be rescheduled after the court rules on the pending motions for reconsideration and for class certification. Xcel Energy has concluded that a loss is remote for the remaining lawsuit. Rate Matters MISO ROE Complaints — In November 2013 and February 2015, customer groups filed two ROE complaints against MISO TOs, which includes NSP-Minnesota and NSP-Wisconsin. The first complaint requested a reduction in base ROE transmission formula rates from 12.38% to 9.15% for the time period of Nov. 12, 2013 to Feb. 11, 2015, and removal of ROE adders (including those for RTO membership). The second complaint requested, for a subsequent time period, a base ROE reduction from 12.38% to 8.67%. In September 2016, the FERC issued an order (Opinion No. 551) granting a 10.32% base ROE effective for the first complaint period of Nov. 12, 2013 to Feb. 11, 2015 and subsequent to the date of the order. The D.C Circuit subsequently vacated and remanded Opinion No. 551. In November 2019, the FERC issued an order (Opinion No. 569), which set the MISO base ROE at 9.88%, effective Sept. 28, 2016 and for the first complaint period. The FERC also dismissed the second complaint. In December 2019, MISO TOs filed a request for rehearing regarding the new ROE methodology announced in Opinion No. 569. Customers also filed requests for rehearing claiming, among other points, that the FERC erred by dismissing the second complaint without refunds. In May 2020, the FERC issued an order (Opinion No. 569-A) which granted rehearing in part to Opinion 569 and further refined the FERC’s ROE methodology, most significantly to incorporate the risk premium model (in addition to the discounted cash flow and capital asset pricing models), resulting in a new base ROE of 10.02%, effective Sept. 28, 2016 and for the first complaint period. The FERC also affirmed its decision in Opinion No. 569 to dismiss the second complaint. In November 2020, the FERC issued an order (Opinion No. 569-B) in response to rehearing requests. The FERC corrected certain inputs to its ROE calculation model, did not change the ROE effective Sept. 28, 2016, and for the first MISO complaint period and upheld its decision to deny refunds for the second complaint period. NSP-Minnesota has recognized a liability for its best estimate of final refunds to customers. Each 10 basis point reduction in ROE for the first complaint period, second complaint period, and subsequent period relative to amounts accrued would reduce Xcel Energy’s net income by $1 million, $1 million, and $2 million, respectively. The MISO TOs and various parties have filed petitions for review of Opinion Nos. 569, 569-A and 569-B at the D.C. Circuit with initial briefs filed in March 2021. A hearing is expected in the fourth quarter of 2021 with a decision anticipated in the first half of 2022. FERC NOPR on ROE Incentive Adders — In April 2021, the FERC issued a NOPR proposing to limit collection of ROE incentive adders for RTO membership to the first three years after an entity begins participation in an RTO. If adopted as a final rule, following a comment period expected to be complete by the end of 2021 or 2022, NSP-Wisconsin would p rospectively discontinue charging their current 0.5% ROE incentive adders. Amounts related to a discontinuance of the adder would ultimately be offset by an increase in retail rates, subject to future rate cases. Environmental MGP, Landfill and Disposal Sites NSP-Wisconsin is investigating, remediating or performing post-closure actions at three MGP, landfill or other disposal sites across its service territories. NSP-Wisconsin has recognized its best estimate of costs/liabilities from final resolution of these issues, however, the outcome and timing is unknown. In addition, there may be insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of costs incurred.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2021
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) 2021 2020 Regulated Electric Total revenues (a) $ 252 $ 236 Net income 38 40 Regulated Natural Gas Operating revenues — external $ 22 $ 15 Intersegment revenue 1 — Total revenues $ 23 $ 15 Net loss (4) (2) All Other Net income $ 2 $ 2 Consolidated Total Total revenues (a) $ 275 $ 251 Reconciling eliminations (1) — Total operating revenues $ 274 $ 251 Net income 36 40 (a) Total revenues include $49 million and $41 million of affiliate electric revenue for the three months ended Sept. 30, 2021 and 2020, respectively. Nine Months Ended Sept. 30 (Millions of Dollars) 2021 2020 Regulated Electric Total revenues (a) $ 700 $ 647 Net income 77 81 Regulated Natural Gas Operating revenues — external $ 110 $ 79 Intersegment revenue 1 — Total revenues $ 111 $ 79 Net income 3 3 All Other Net income $ 2 $ 1 Consolidated Total Total revenues (a) $ 811 $ 726 Reconciling eliminations (1) — Total operating revenues $ 810 $ 726 Net income 82 85

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Accounts receivable, net Accounts receivable $ 68 $ 78 Less allowance for bad debts (8) (8) Accounts receivable, net $ 60 $ 70
Inventories	(Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Inventories Materials and supplies $ 7 $ 7 Fuel 6 4 Natural gas 10 4 Total inventories $ 23 $ 15
Property, Plant and Equipment, Net	(Millions of dollars) Sept. 30, 2021 Dec. 31, 2020 Property, plant and equipment, net Electric plant $ 3,287 $ 3,197 Natural gas plant 411 391 Common and other property 226 221 Construction work in progress 122 71 Total property, plant and equipment 4,046 3,880 Less accumulated depreciation (1,456) (1,396) Property, plant and equipment, net $ 2,590 $ 2,484

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	As of Sept. 30, 2021, 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 June 2024. (b) Includes outstanding commercial paper.
Money Pool
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Money pool borrowings for NSP-Wisconsin: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2021 Year Ended Dec. 31, 2020 Borrowing limit $ 150 $ — Amount outstanding at period end — — Average amount outstanding 11 — Maximum amount outstanding 60 — Weighted average interest rate, computed on a daily basis 0.05 % N/A 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 for NSP-Wisconsin: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2021 Year Ended Dec. 31, 2020 Borrowing limit $ 150 $ 150 Amount outstanding at period end — 19 Average amount outstanding — 30 Maximum amount outstanding — 95 Weighted average interest rate, computed on a daily basis N/A 1.59 % Weighted average interest rate at period end N/A 0.17

Revenues (Tables)

Revenues (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	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 $ 73 $ 8 $ 81 C&I 126 12 138 Other 2 — 2 Total retail 201 20 221 Interchange 48 — 48 Other — 2 2 Total revenue from contracts with customers 249 22 271 Alternative revenue and other 3 — 3 Total revenues $ 252 $ 22 $ 274 Three Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 71 $ 7 $ 78 C&I 119 6 125 Other 1 — 1 Total retail 191 13 204 Interchange 41 — 41 Other 1 1 2 Total revenue from contracts with customers 233 14 247 Alternative revenue and other 3 1 4 Total revenues $ 236 $ 15 $ 251 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 208 $ 54 $ 262 C&I 336 51 387 Other 7 — 7 Total retail 551 105 656 Interchange 140 — 140 Other — 4 4 Total revenue from contracts with customers 691 109 800 Alternative revenue and other 9 1 10 Total revenues $ 700 $ 110 $ 810 Nine Months Ended (Millions of Dollars) Electric Natural Gas Total Major revenue types Revenue from contracts with customers: Residential $ 195 $ 43 $ 238 C&I 313 32 345 Other 5 — 5 Total retail 513 75 588 Interchange 123 — 123 Other 1 3 4 Total revenue from contracts with customers 637 78 715 Alternative revenue and other 10 1 11 Total revenues $ 647 $ 79 $ 726

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Difference between the statutory rate and ETR: Nine Months Ended Sept. 30 2021 2020 (a) Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Increases (decreases) in tax from: Plant regulatory differences (b) (3.9) (19.6) Amortization of excess nonplant deferred taxes — (12.8) Tax credits, net of NOL & tax credit allowances (1.0) (1.6) Other (net) (1.1) 0.5 Effective income tax rate 21.2 % (6.3) % (a) Prior periods have been restated to conform to current year presentation.
Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]	Federal Audits — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s consolidated federal income tax returns expire as follows: Tax Years Expiration 2014 - 2016 December 2022 2018 September 2022
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs. temporary: (Millions of Dollars) Sept. 30, 2021 Dec. 31, 2020 Unrecognized tax benefit — Permanent tax positions $ 2 $ 1 Unrecognized tax benefit — Temporary tax positions 1 1 Total unrecognized tax benefit $ 3 $ 2
Tax Benefits Associated with NOL and Tax Credit Carryforwards	Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) Sept. 30, 2021 Dec. 31, 2020 NOL and tax credit carryforwards $ (2) $ (2)

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	Recurring Fair Value Measurements — NSP-Wisconsin's derivative assets measured at fair value on a recurring basis were as follows: Sept. 30, 2021 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 4 $ — $ 4 $ — $ 4 Dec. 31, 2020 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 1 $ — $ 1 $ — $ 1 (a) NSP-Wisconsin nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2021 and Dec. 31, 2020. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) Included in prepayments and other current assets balance of $8 million at Sept. 30, 2021 and $7 million at Dec. 31, 2020 on the consolidated balance sheets.
Carrying Amount and Fair Value of Long-term Debt	Other financial instruments for which the carrying amount did not equal fair value: Sept. 30, 2021 Dec. 31, 2020 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 1,006 $ 1,173 $ 906 $ 1,124

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost Three Months Ended Sept. 30 2021 2020 (Millions of Dollars) Pension Benefits Service cost $ 1 $ 1 Interest cost (a) 1 1 Expected return on plan assets (a) (2) (2) Amortization of net loss (a) 2 1 Settlement charge (b) 3 — Net periodic benefit cost $ 5 $ 1 Effects of regulation (2) 2 Net benefit cost recognized for financial reporting $ 3 $ 3 Nine Months Ended Sept. 30 2021 2020 (Millions of Dollars) Pension Benefits Service cost $ 4 $ 3 Interest cost (a) 3 4 Expected return on plan assets (a) (6) (6) Amortization of net loss (a) 4 4 Settlement charge (b) 3 — Net periodic benefit cost $ 8 $ 5 Effects of regulation (2) 5 Net benefit cost recognized for financial reporting $ 6 $ 10 (a) The components of net periodic cost other than the service cost component are included in the line item “Other expense, 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 third quarter as a result of lump-sum distributions during the 2021 plan year, NSP-Wisconsin recorded a pension settlement charge of $3 million, the majority of which was not recognized in earnings due to the effects of regulation.	[1]
[1]	The components of net periodic cost other than the service cost component are included in the line item “Other expense, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset.

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	NSP-Wisconsin's segment information: Three Months Ended Sept. 30 (Millions of Dollars) 2021 2020 Regulated Electric Total revenues (a) $ 252 $ 236 Net income 38 40 Regulated Natural Gas Operating revenues — external $ 22 $ 15 Intersegment revenue 1 — Total revenues $ 23 $ 15 Net loss (4) (2) All Other Net income $ 2 $ 2 Consolidated Total Total revenues (a) $ 275 $ 251 Reconciling eliminations (1) — Total operating revenues $ 274 $ 251 Net income 36 40 (a) Total revenues include $49 million and $41 million of affiliate electric revenue for the three months ended Sept. 30, 2021 and 2020, respectively. Nine Months Ended Sept. 30 (Millions of Dollars) 2021 2020 Regulated Electric Total revenues (a) $ 700 $ 647 Net income 77 81 Regulated Natural Gas Operating revenues — external $ 110 $ 79 Intersegment revenue 1 — Total revenues $ 111 $ 79 Net income 3 3 All Other Net income $ 2 $ 1 Consolidated Total Total revenues (a) $ 811 $ 726 Reconciling eliminations (1) — Total operating revenues $ 810 $ 726 Net income 82 85 (a) Total revenues include $141 million and $123 million of affiliate electric revenue for the nine months ended Sept. 30, 2021 and 2020, respectively.

Selected Balance Sheet Data - A

Selected Balance Sheet Data - Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, Net
Accounts receivable	$ 68	$ 78
Less allowance for bad debts	(8)	(8)
Accounts receivable, net	$ 60	$ 70

Selected Balance Sheet Data - I

Selected Balance Sheet Data - Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Public Utilities, Inventory [Line Items]
Total Inventories	$ 23	$ 15
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	7	7
Fuel
Public Utilities, Inventory [Line Items]
Inventories	6	4
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 10	$ 4

Selected Balance Sheet Data - P

Selected Balance Sheet Data - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,046	$ 3,880
Less accumulated depreciation	(1,456)	(1,396)
Property, plant and equipment, net	2,590	2,484
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,287	3,197
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	411	391
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	226	221
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 122	$ 71

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments, Commercial Paper (Details) - USD ($)		3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
		Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Amount outstanding at period end		$ 0		$ 0	$ 19,000,000
Credit Facility
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]	150,000,000		150,000,000
Long-term Line of Credit		0		0	0
Payable to Affiliates
Short-term Debt [Line Items]
Notes Payable, Related Parties, Current		0		0	0
Commercial Paper
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150,000,000		150,000,000	150,000,000
Amount outstanding at period end		0		0	19,000,000
Average amount outstanding				0	30,000,000
Maximum amount outstanding				0	$ 95,000,000
Weighted average interest rate, computed on a daily basis					1.59%
Weighted average interest rate at period end					0.17%
Money Pool
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150,000,000		150,000,000	$ 0
Amount outstanding at period end		0		$ 0	0
Average amount outstanding		11,000,000			$ 0
Maximum amount outstanding		$ 60,000,000	$ 0
Weighted average interest rate, computed on a daily basis		0.05%
[1]	Expires in June 2024.

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments, Letters of Credit (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Period	1 year
Amount outstanding at period end	$ 0	$ 19,000,000
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) - Credit Facility - USD ($)		Sep. 30, 2021	Dec. 31, 2020
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 June 2024.
[2]	Includes outstanding commercial paper.

Borrowings and Other Financin_6

Borrowings and Other Financing Instruments (Details) - USD ($)	Sep. 30, 2021	Mar. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Clearwater Borrowings	$ 0		$ 0
Series Due May 1, 2051 [Domain] | Bonds [Member] | NSP-Wisconsin [Member]
Short-term Debt [Line Items]
Debt Instrument, Face Amount		$ 100,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.82%
Payable to Affiliates
Short-term Debt [Line Items]
Notes Payable, Related Parties, Current	$ 0		$ 0

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 274	$ 251	$ 810	$ 726
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	252	236	700	647
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	22	15	110	79
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	221	204	656	588
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	78	262	238
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	138	125	387	345
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	1	7	5
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	201	191	551	513
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	73	71	208	195
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	126	119	336	313
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	1	7	5
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	13	105	75
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8	7	54	43
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	6	51	32
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Interchange
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	48	41	140	123
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	48	41	140	123
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	4
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	0	1
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	1	4	3
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	271	247	800	715
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	249	233	691	637
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	14	109	78
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	4	10	11
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	3	9	10
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 0	$ 1	$ 1	$ 1

Income Taxes (Details)

Income Taxes (Details) - USD ($)		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	[1]	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Income Tax Penalties Accrued		$ 0			$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		6.20%	6.20%
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[2]	(3.90%)	(19.60%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Percent		0.00%	(12.80%)
Regulatory difference - tax credits and tax credit and NOL allowances (net)		(1.00%)	(1.60%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		(1.10%)	0.50%
Effective Income Tax Rate Reconciliation, Percent		21.20%	(6.30%)
[1]	Prior periods have been restated to conform to current year presentation.
[2]	Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.

Income Taxes Unrecognized Benef

Income Taxes Unrecognized Benefits (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Tax Benefits Associated With Nol And Tax Credit Carryforwards	$ 2,000,000	$ 2,000,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,000,000	1,000,000
Unrecognized Tax Benefits That Would Not Impact Effective Tax Rate	1,000,000	1,000,000
Total unrecognized tax benefit	3,000,000	2,000,000
Decrease in Unrecognized Tax Benefits is Reasonably Possible	1,000,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 0	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Interest Rate Derivatives (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Interest Rate Swap
Derivative [Line Items]
Derivative Liability, Notional Amount	$ 0	$ 0	$ 0
Natural Gas Commodity | Other Derivative Instruments
Derivative [Line Items]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	$ 3	$ 3

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Impact of Derivative Activities on Income (Details) MMBTU in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021USD ($)MMBTU	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)MMBTU	Sep. 30, 2020USD ($)	Dec. 31, 2020MMBTU
Financial Impact of Qualifying Fair Value Hedges on Earnings [Abstract]
Derivative instruments designated as fair value hedges		$ 0	$ 0	$ 0	$ 0
Natural Gas Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU	[1],[2]	2		2		0
Other Derivative Instruments | Natural Gas Commodity
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		$ 0	$ 0	$ (1)	$ (1)
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities		$ 3		$ 3
[1]	Amounts are not reflective of net positions in the underlying commodities.
[2]	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Prepayments and other		$ 8	$ 7
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		4	1
Netting	[1]	0	0
Derivative Asset, Net	[2]	4	1
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		4	1
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		$ 0	$ 0
[1]	NSP-Wisconsin nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2021 and Dec. 31, 2020. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.
[2]	Included in prepayments and other current assets balance of $8 million at Sept. 30, 2021 and $7 million at Dec. 31, 2020 on the consolidated balance sheets.

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	$ 1,006	$ 906
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 1,173	$ 1,124

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) - Pension Plan [Member] $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
		Jan. 31, 2021USD ($)Plan	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Components of Net Periodic Benefit Cost [Abstract]
Service cost			$ 1	$ 1	$ 4	$ 3
Interest cost (a)	[1]		1	1	3	4
Expected return on plan assets (a)	[1]		(2)	(2)	(6)	(6)
Amortization of net loss (a)	[1]		2	1	4	4
Net periodic benefit cost			5	1	8	5
Effects of regulation			(2)	2	(2)	5
Net benefit cost recognized for financial reporting			3	3	6	10
Contributions to pension plans		$ 5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]		$ 3	$ 0	$ 3	$ 0
Parent Company [Member]
Components of Net Periodic Benefit Cost [Abstract]
Contributions to pension plans		$ 125
Number of Xcel Energy's pension plans to which contributions were made | Plan		4
[1]	The components of net periodic cost other than the service cost component are included in the line item “Other expense, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset.
[2]	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 third quarter as a result of lump-sum distributions during the 2021 plan year, NSP-Wisconsin recorded a pension settlement charge of $3 million, the majority of which was not recognized in earnings due to the effects of regulation

Commitments and Contingencies G

Commitments and Contingencies Gas Trading Litigation (Details) number in Millions	Oct. 25, 2021USD ($)	Sep. 30, 2021
Loss Contingencies [Line Items]
Active gas litigation cases	$ 1
Breckenridge Litigation
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number		3

MISO ROE Complaints (Details)

MISO ROE Complaints (Details) - Federal Energy Regulatory Commission (FERC)	1 Months Ended		3 Months Ended	7 Months Ended	11 Months Ended	17 Months Ended
	Feb. 28, 2015	Nov. 30, 2013	Jun. 30, 2017	Dec. 31, 2020	Mar. 31, 2021	Mar. 31, 2021	Sep. 30, 2021
NSP Minnesota, NSP Wisconsin and SPS
Rate Matters [Abstract]
ROE incentive adders related to FERC NOPR							0.50%
FERC Proceeding, MISO ROE Complaint | NSP Minnesota and NSP Wisconsin [Member] [Member]
Rate Matters [Abstract]
Basis Point Reduction - Third Complaint				200000000.00%
Basis Point Reduction - Second Complaint				100000000.00%
Basis Point Reduction - First Complaint				100000000.00%
Public Utilities, Base Return On Equity Charged To Customers Through Transmission Formula Rates	12.38%	12.38%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Recommended By Third Parties	8.67%	9.15%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Approved			10.32%
Public Utilities, ROE developed with new approach						9.88%
Public Utilities, ROE New Base, Complaint Number 1					10.02%

MGP, Landfill and Disposal Site

MGP, Landfill and Disposal Sites (Details)	Sep. 30, 2021
Other MGP, Landfill, or Disposal Sites [Domain]
Site Contingency [Line Items]
Number of identified MGP sites under current investigation and/or remediation	3

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2021		Sep. 30, 2020		Sep. 30, 2021		Sep. 30, 2020
Segment Reporting Information [Line Items]
Net income	$ 36		$ 40		$ 82		$ 85
Regulated and Unregulated Operating Revenue	274		251		810		726
Affiliate Revenue	49		41		141		123
Natural gas	22		15		110		79
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	275	[1]	251	[1]	811	[2]	726	[2]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(1)		0		(1)		0
Regulated Electric
Segment Reporting Information [Line Items]
Net income	38		40		77		81
Regulated Electric | Total revenues
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	252	[1]	236	[1]	700	[2]	647	[2]
Regulated Natural Gas
Segment Reporting Information [Line Items]
Net income	(4)		(2)		3		3
Revenues Including Intersegment Revenues	23		15		111		79
Regulated Natural Gas | Total revenues
Segment Reporting Information [Line Items]
Natural gas	22		15		110		79
Regulated Natural Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Natural gas	1		0		1		0
All Other
Segment Reporting Information [Line Items]
Net income	$ 2		$ 2		$ 2		$ 1
[1]	Total revenues include $49 million and $41 million of affiliate electric revenue for the three months ended Sept. 30, 2021 and 2020, respectively.
[2]	Total revenues include $141 million and $123 million of affiliate electric revenue for the nine months ended Sept. 30, 2021 and 2020, respectively.