Southwestern Public Service 10-K 23 Feb 22 2021 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 23, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-03789
Entity Incorporation, State or Country Code	NM
Entity Tax Identification Number	75-0575400
Entity Address, Address Line One	790 South Buchanan Street,
Entity Address, City or Town	Amarillo,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	79101
City Area Code	(303)
Local Phone Number	571-7511
Entity Well-Known Season Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		100
Entity Registrant Name	SOUTHWESTERN PUBLIC SERVICE CO
Entity Central Index Key	0000092521
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Public Float			$ 0

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Auditor [Line Items]
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Firm ID	34
Auditor Location	Minneapolis, Minnesota

Accounting Pronouncements

Accounting Pronouncements	12 Months Ended
	Dec. 31, 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.

STATEMENTS OF INCOME

STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues [Abstract]
Operating revenue	$ 2,465	$ 1,870	$ 1,826
Operating expenses
Electric fuel and purchased power	1,432	835	875
Operating and maintenance expenses	271	275	285
Demand side management program expenses	17	16	17
Depreciation and amortization	300	295	230
Taxes (other than income taxes)	79	90	72
Total operating expenses	2,099	1,511	1,479
Operating income	366	359	347
Other income (expense), net	1	(2)	2
Allowance for funds used during construction — equity	4	33	27
Interest charges and financing costs
Interest Expense	114	119	99
Allowance for funds used during construction — debt	(2)	(14)	(12)
Total interest charges and financing costs	112	105	87
Income before income taxes	259	285	289
Income taxes	(59)	(10)	26
Net income	$ 318	$ 295	$ 263

STATEMENTS OF INCOME (Parenthet

STATEMENTS OF INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Other financing costs	$ 4	$ 4	$ 3

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net Income (Loss) Attributable to Parent	$ 318	$ 295	$ 263
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	303	298	232
Deferred income taxes	(47)	22	29
Allowance for equity funds used during construction	(4)	(33)	(27)
Provision for bad debts	6	6	6
Changes in operating assets and liabilities:
Accounts receivable	(29)	(14)	(9)
Increase (Decrease) in Accrued Unbilled Revenues	(10)	0	(1)
Inventories	(21)	(35)	(21)
Prepayments and other	16	(14)	3
Accounts payable	4	8	(9)
Net regulatory assets and liabilities	(154)	(115)	14
Other current liabilities	(1)	13	6
Pension and other employee benefit obligations	(18)	(16)	(18)
Other, net	(4)	(1)	5
Net cash provided by operating activities	359	414	473
Investing activities
Utility capital/construction expenditures	(580)	(1,142)	(844)
Investments in utility money pool arrangement	(83)	(4)	(133)
Receipts from utility money pool arrangement	83	4	133
Net cash used in investing activities	(580)	(1,142)	(844)
Financing activities
(Repayments of) proceeds from short-term borrowings, net	(113)	250	(42)
Proceeds from issuance of long-term debt	247	343	292
Borrowings under utility money pool arrangement	539	561	296
Repayments under utility money pool arrangement	(448)	(561)	(296)
Capital contributions from parent	301	438	426
Dividends paid to parent	(310)	(313)	(333)
Net cash provided by financing activities	216	718	343
Net change in cash and cash equivalents	(5)	(10)	(28)
Cash and cash equivalents at beginning of period	6	16	44
Cash and cash equivalents at end of period	1	6	16
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(108)	(98)	(84)
Cash paid for income taxes, net	21	10	12
Supplemental disclosure of non-cash investing transactions:
Accrued property, plant and equipment additions	37	99	95
Inventory transfers to plant, property and equipment	6	31	23
Operating lease right-of-use assets	0	0	548
Allowance for Funds Used During Construction, Investing Activities	$ 4	$ 33	$ 27

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 1	$ 6
Accounts receivable, net	115	94
Accounts receivable from affiliates	9	9
Accrued unbilled revenues	125	114
Inventories	51	36
Regulatory assets	193	76
Derivative instruments	30	10
Prepaid taxes	3	18
Prepayments and other	21	20
Total current assets	548	383
Property, plant and equipment, net	7,838	7,603
Other assets
Regulatory assets	380	357
Derivative instruments	6	9
Operating lease right-of-use assets	463	492
Other	27	15
Total other assets	876	873
Total assets	9,262	8,859
Current liabilities
Short-term debt	137	250
Borrowings under utility money pool arrangement	91	0
Accounts payable	172	198
Accounts payable to affiliates	16	17
Regulatory liabilities	54	57
Taxes accrued	47	54
Accrued interest	30	29
Dividends payable to parent	58	54
Derivative instruments	4	4
Operating lease liabilities	30	28
Other	24	25
Total current liabilities	663	716
Deferred credits and other liabilities
Deferred income taxes	702	725
Regulatory liabilities	709	718
Asset retirement obligations	116	112
Derivative instruments	6	9
Pension and employee benefit obligations	8	42
Operating lease liabilities	434	463
Other	8	12
Total deferred credits and other liabilities	1,983	2,081
Commitments and contingencies
Capitalization
Long-term debt	3,013	2,764
Common Stock, Value, Issued	0	0
Additional paid in capital	3,091	2,790
Retained earnings	513	509
Accumulated other comprehensive loss	(1)	(1)
Total common stockholder's equity	3,603	3,298
Total liabilities and equity	$ 9,262	$ 8,859

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common Stock, Shares Authorized	200	200
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares, Outstanding	100	100

STATEMENTS OF COMMON STOCKHOLDE

STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common stock	Additional Paid In Capital	Retained Earnings	AOCI Attributable to Parent
Beginning Balance (in shares) at Dec. 31, 2018		100
Beginning Balance at Dec. 31, 2018	$ 2,537	$ 0	$ 1,932	$ 606	$ (1)
Increase (Decrease) in Stockholder's Equity
Net Income (Loss) Attributable to Parent	263			263
Common dividends declared to parent	(334)			(334)
Contribution of capital by parent	419		419
Ending Balance (in shares) at Dec. 31, 2019		100
Ending Balance at Dec. 31, 2019	2,885	$ 0	2,351	535	(1)
Increase (Decrease) in Stockholder's Equity
Net Income (Loss) Attributable to Parent	295			295
Common dividends declared to parent	(321)			(321)
Contribution of capital by parent	$ 439		439
Ending Balance (in shares) at Dec. 31, 2020	100	100
Ending Balance at Dec. 31, 2020	$ 3,298	$ 0	2,790	509	(1)
Increase (Decrease) in Stockholder's Equity
Net Income (Loss) Attributable to Parent	318			318
Common dividends declared to parent	(314)			(314)
Contribution of capital by parent	$ 301		301
Ending Balance (in shares) at Dec. 31, 2021	100	100
Ending Balance at Dec. 31, 2021	$ 3,603	$ 0	$ 3,091	$ 513	$ (1)

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Federal Tax Loss Carryback Claims — In 2020, Xcel Energy identified certain expenses related to tax years 2009 - 2011 that qualify for an extended carryback claim. SPS is not expected to accrue any income tax expense related to this adjustment. Federal Audit — SPS is a member of Xcel Energy affiliated group that files a consolidated federal income tax return. The statute of limitations applicable to Xcel Energy’s consolidated federal tax returns expire as follows: Tax Year(s) Expiration 2014 - 2016 December 2022 2018 September 2022 Additionally, the statute of limitations related to the federal tax credit carryforwards will remain open until those credits are utilized in subsequent returns. Further, the statute of limitations related to the additional 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 — SPS is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of Dec. 31, 2021, SPS’ earliest open tax year that is subject to examination by state taxing authorities under applicable statutes of limitations is 2016. In April 2021, Texas began an audit of tax years 2016 - 2019. As of Dec. 31, 2021, no material adjustments have been proposed. Unrecognized Tax Benefits — 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) Dec. 31, 2021 Dec. 31, 2020 Unrecognized tax benefit — Permanent tax positions $ 4 $ 3 Unrecognized tax benefit — Temporary tax positions 4 4 Total unrecognized tax benefit $ 8 $ 7 Changes in unrecognized tax benefits: (Millions of Dollars) 2021 2020 2019 Balance at Jan. 1 $ 7 $ 5 $ 5 Additions based on tax positions related to the current year 1 1 — Additions for tax positions of prior years — 5 — Reductions for tax positions of prior years — (4) — Balance at Dec. 31 $ 8 $ 7 $ 5 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 NOL and tax credit carryforwards $ (7) $ (6) As the IRS progresses its review of the tax loss carryback claim and as state audits progress, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $5 million in the next 12 months. Payable for interest related to unrecognized tax benefits is partially offset by the interest benefit associated with NOL and tax credit carryforwards. Interest payable related to unrecognized tax benefits: (Millions of Dollars) 2021 2020 2019 (Payable) receivable for interest related to unrecognized tax benefits at Jan. 1 $ (1) $ 1 $ 1 Interest expense related to unrecognized tax benefits — (2) — (Payable) receivable for interest related to unrecognized tax benefits at Dec. 31 $ (1) $ (1) $ 1 No amounts were accrued for penalties related to unrecognized tax benefits as of Dec. 31, 2021, 2020 or 2019. Other Income Tax Matters — NOL amounts represent the tax loss that is carried forward and tax credits represent the deferred tax asset. NOL and tax credit carryforwards as of Dec. 31 were as follows: (Millions of Dollars) 2021 2020 Federal NOL carryforward $ 336 $ — Federal tax credit carryforwards 187 83 State NOL carryforwards 111 1 Federal carryforward periods expire between 2031 and 2041 and state carryforward periods expire starting 2034. Total income tax expense from operations differs from the amount computed by applying the statutory federal income tax rate to income before income tax expense. Effective income tax rate for years ended Dec. 31: 2021 2020 (a) 2019 (a) Federal statutory rate 21.0 % 21.0 % 21.0 % State income tax on pretax income, net of federal tax effect 2.5 2.3 2.2 Increases (decreases) in tax from: Wind PTCs (39.7) (18.3) (7.9) Plant regulatory differences (b) (4.8) (6.4) (5.0) Amortization of excess nonplant deferred taxes (1.1) (0.8) (0.9) Change in unrecognized tax benefits 0.5 0.3 0.2 Other, net (1.2) (1.6) (0.6) Effective income tax rate (22.8) % (3.5) % 9.0 % (a) Prior periods have been reclassified 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. Components of income tax expense for years ended Dec. 31: (Millions of Dollars) 2021 2020 2019 Current federal tax benefit $ (11) $ (31) $ (4) Current state tax (benefit) expense (1) (1) 1 Current change in unrecognized tax expense — — — Deferred federal tax (benefit) expense (57) 13 22 Deferred state tax expense 9 8 6 Deferred change in unrecognized tax expense 1 1 1 Total income tax (benefit) expense $ (59) $ (10) $ 26 Components of deferred income tax expense as of Dec. 31: (Millions of Dollars) 2021 2020 2019 Deferred tax (benefit) expense excluding items below $ (23) $ 53 $ 53 Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities (24) (31) (24) Deferred tax (benefit) expense $ (47) $ 22 $ 29 Components of the net deferred tax liability as of Dec. 31: (Millions of Dollars) 2021 2020 (a) Deferred tax liabilities: Differences between book and tax bases of property $ 942 $ 838 Operating lease assets 103 109 Regulatory assets 65 59 Deferred fuel costs 34 (9) Pension expense 34 33 Other 2 2 Total deferred tax liabilities $ 1,180 $ 1,032 Deferred tax assets: Operating lease liabilities $ 103 $ 109 Regulatory liabilities 98 104 Tax credit carryforward 187 83 NOL carryforward 76 — Other employee benefits 7 7 Other 7 4 Total deferred tax assets 478 307 Net deferred tax liability $ 702 $ 725 (a) Prior periods have been reclassified to conform to current year presentation.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Legal SPS 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 SPS’ financial statements. Legal fees are generally expensed as incurred. Rate Matters SPS 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. SPP OATT Upgrade Costs — Costs of transmission upgrades may be recovered from other SPP customers whose transmission service depends on capacity enabled by the upgrade under the SPP OATT. SPP had not been charging its customers for these upgrades, even though the SPP OATT had allowed SPP to do so since 2008. In 2016, the FERC granted SPP’s request to recover these previously unbilled charges and SPP subsequently billed SPS approximately $13 million. In July 2018, SPS’ appeal to the D.C. Circuit over the FERC rulings granting SPP the right to recover previously unbilled charges was remanded to the FERC. In February 2019, the FERC reversed its 2016 decision and ordered SPP to refund charges retroactively collected from its transmission customers, including SPS, related to periods before September 2015. In March 2020, SPP and Oklahoma Gas & Electric separately filed petitions for review of the FERC’s orders at the D.C. Circuit. In August 2021, the D.C Circuit issued a decision denying these appeals and upholding the FERC’s orders. Refunds received by SPS are expected to be given back to SPS customers through future rates. The timing of these refunds is uncertain. In October 2017, SPS filed a separate related complaint asserting SPP assessed upgrade charges to SPS in violation of the SPP OATT. In March 2018, the FERC issued an order denying the SPS complaint. SPS filed a request for rehearing in April 2018. The FERC issued a tolling order granting a rehearing for further consideration in May 2018. If SPS’ complaint results in additional charges or refunds, SPS will seek to recover or refund the amount through future SPS customer rates. In October 2020, SPS filed a petition for review of the FERC’s March 2018 order and May 2018 tolling order at the D.C. Circuit. FERC has asked that this appeal be stayed until early 2022, in order to provide FERC with time to issue an order on SPS’ April 2018 rehearing request. FERC’s order is expected in the first quarter of 2022. The D.C. Circuit appeal may resume after that FERC order is issued. Wind Operating Commitments — PUCT and NMPRC orders related to the Hale and Sagamore wind projects included certain operating and savings minimums. In general, annual generation must exceed a net capacity factor of 48%. If annual generation is below the guaranteed level, SPS would be obligated to refund an amount equal to foregone PTCs and fuel savings. Additionally, retail customer savings must exceed project costs included in base rates over the first ten years of operations. SPS would be required to refund excess costs, if any, after ten years of operations. As of Dec. 31, 2021, the full-year net capacity factor was 48.4%, resulting in no refund liability for 2021. Contract Termination — SPS and LP&L are parties to a 25-year, 170 MW partial requirements contract. In May 2021, SPS and LP&L finalized a settlement which would terminate the contract upon LP&L’s move from the SPP to the ERCOT (expected in 2023). The settlement agreement requires LP&L to pay SPS $78 million (lump sum or annual installments), to the benefit of SPS’ remaining customers. LP&L would remain obligated to pay for SPP transmission charges associated with LP&L’s load in SPP. The settlement agreement is subject to approval by the PUCT and FERC. Environmental New and changing federal and state environmental mandates can create financial liabilities for SPS, 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. SPS may sometimes pay all or a portion of the cost to remediate sites where past activities of SPS’ 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 SPS is alleged to have sent wastes to that site. Historical MGP, Landfill and Disposal Sites SPS is remediating a former disposal site. SPS has recognized its best estimate of costs/liabilities from final resolution of these issues; however, the outcome and timing are unknown. In addition, there may be insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of costs incurred. Environmental Requirements — Water and Waste Federal CWA Waters of the U.S. Rule — SPS is monitoring ongoing changes to the definition of Waters of the U.S. under the CWA. Regardless of which definition is applicable in the states in which we operate, SPS does not anticipate that compliance costs will be material. Federal CWA ELG — In 2015, the EPA issued a final ELG rule for power plants that discharge treated effluent to surface waters as well as utility-owned landfills that receive coal combustion residuals. In October 2020, the EPA published a final rule revising the regulations. SPS anticipates that compliance costs will not be material and will be fully recoverable through regulatory mechanisms. Environmental Requirements — Air Regional Haze Rules — The regional haze program requires SO 2 , nitrogen oxide and particulate matter emission controls at power plants to reduce visibility impairment in national parks and wilderness areas. The program includes BART and reasonable further progress. Texas’ first regional haze plan has undergone federal review. All states are now subject to a second round of regional haze planning/rulemaking, focusing on additional reductions to meet reasonable progress requirements. Any additional impacts to SPS facilities are expected to be minimal. BART Determination for Texas: The EPA has issued a revised final rule adopting a BART alternative Texas only SO 2 trading program that applies to all Harrington and Tolk units. Under the trading program, SPS expects the allowance allocations to be sufficient for SO 2 emissions. The anticipated costs of compliance are not expected to have a material impact; and SPS believes that compliance costs would be recoverable through regulatory mechanisms. Several parties have challenged whether the final rule issued by the EPA should be considered to have met the requirements imposed in a Consent Decree entered by the D.C. Circuit that established deadlines for the EPA to take final action on state regional haze plan submissions. The court has required status reports from the parties while the EPA works on the reconsideration rulemaking. In December 2017, the National Parks Conservation Association, Sierra Club, and Environmental Defense Fund appealed the EPA’s 2017 final BART rule to the Fifth Circuit and filed a petition for administrative reconsideration. The court has held the litigation in abeyance while the EPA decided whether to reconsider the rule. In August 2018, the EPA started a reconsideration rulemaking. The EPA reaffirmed the rule in August 2020 with minor changes. The 2020 EPA Action has been challenged. All pending actions could be consolidated and may proceed in the Fifth Circuit or the D.C. Circuit, where a parallel challenge has been filed. The timing of final decisions is unclear. Reasonable Progress Rule: In 2016, the EPA adopted a final rule establishing a federal implementation plan for reasonable further progress under the regional haze program for the state of Texas. The rule imposes SO 2 emission limitations that would require the installation of dry scrubbers on Tolk Units 1 and 2; compliance would have been required by February 2021. Investment costs associated with dry scrubbers could be $600 million. SPS appealed the EPA’s decision and obtained a stay of the final rule. In March 2017, the Fifth Circuit remanded the rule to the EPA for reconsideration, leaving the stay in effect. In a future rulemaking, the EPA will address whether SO 2 emission reductions beyond those required in the BART alternative rule referenced above are needed at Tolk under the “reasonable progress” requirements. As states are now proceeding with the second regional haze planning period, the EPA may choose not to act on the remanded rule. Implementation of the NAAQS for SO 2 — The EPA has designated all areas near SPS’ generating plants as attaining the SO 2 NAAQS with one exception. The EPA issued final designations, which found the area near the Harrington plant as “unclassifiable.” The area near the Harrington plant was monitored for the three years ending in 2019 and the monitoring showed the area to be exceeding the standard. To address this issue, SPS negotiated an order with the TCEQ providing for the end of coal combustion and the conversion of the Harrington plant to a natural gas fueled facility by Jan. 1, 2025. SPS believes compliance costs or the costs of alternative cost-effective generation will be recoverable through regulatory mechanisms and therefore does not expect a material impact on results of operations, financial condition or cash flows. AROs — AROs have been recorded for SPS’ assets. SPS’ AROs were as follows: 2021 (Millions of Dollars) Jan. 1, 2021 Accretion Dec. 31, 2021 (a) Electric Steam and other production $ 52 $ 2 $ 54 Wind 50 2 52 Distribution 10 — 10 Total liability $ 112 $ 4 $ 116 (a) There were no ARO amounts incurred, settled or revised in 2021. 2020 (Millions of Jan. 1, 2020 Amounts Incurred (a) Amounts Settled (b) Accretion Dec. 31, 2020 (c) Electric Steam and other production $ 51 $ — $ (2) $ 3 $ 52 Wind 16 33 — 1 50 Distribution 10 — — — 10 Total liability $ 77 $ 33 $ (2) $ 4 $ 112 (a) Amounts incurred related to the Sagamore wind farm placed in service in 2020. (b) Amounts settled related to asbestos abatement projects. (c) No AROs were revised in 2020. Indeterminate AROs — Outside of the recorded asbestos AROs, other plants or buildings may contain asbestos due to the age of many of SPS’ facilities, but no confirmation or measurement of the cost of removal could be determined as of Dec. 31, 2021. Therefore, an ARO has not been recorded for these facilities. Leases SPS evaluates contracts that may contain leases, including PPAs and arrangements for the use of office space and other facilities, vehicles and equipment. A contract contains a lease if it conveys the exclusive right to control the use of a specific asset. A contract determined to contain a lease is evaluated further to determine if the arrangement is a finance lease. ROU assets represent SPS’ rights to use leased assets. The present value of future operating lease payments is recognized in current and noncurrent operating lease liabilities. These amounts, adjusted for any prepayments or incentives, are recognized as operating lease ROU assets. Most of SPS’ leases do not contain a readily determinable discount rate. Therefore, the present value of future lease payments is generally calculated using the estimated incremental borrowing rate (weighted average of 4.4%). SPS has elected to utilize the practical expedient under which non-lease components, such as asset maintenance costs included in payments, are not deducted from minimum lease payments for the purposes of lease accounting and disclosure. Leases with an initial term of 12 months or less are classified as short-term leases and are not recognized on the balance sheet. Operating lease ROU assets: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 PPAs $ 500 $ 500 Other 45 50 Gross operating lease ROU assets 545 550 Accumulated amortization (82) (58) Net operating lease ROU assets $ 463 $ 492 Components of lease expense: (Millions of Dollars) 2021 2020 2019 Operating leases PPA capacity payments $ 53 $ 48 $ 48 Other operating leases (a) 4 3 5 Total operating lease expense (b) $ 57 $ 51 $ 53 (a) Includes short-term lease expense o f $1 million , $1 million and $2 million for 2021, 2020 and 2019, respectively. (b) PPA capacity payments are included in electric fuel and purchased power on the statements of income. Expense for other operating leases is included in O&M expense. Commitments under operating leases as of Dec. 31, 2021: (Millions of Dollars) PPA (a) (b) Operating Leases Other Operating Leases Total Leases 2022 $ 46 $ 3 $ 49 2023 46 3 49 2024 46 3 49 2025 46 4 50 2026 46 4 50 Thereafter 312 40 352 Total minimum obligation 542 57 599 Interest component of obligation (120) (15) (135) Present value of minimum obligation 422 42 464 Less current portion (30) Noncurrent operating and finance lease liabilities $ 434 Weighted-average remaining lease term in years 12 (a) Amounts do not include PPAs accounted for as executory contracts and/or contingent payments, such as energy payments on renewable PPAs. (b) PPA operating leases contractually expire at various dates through 2033. Non-Lease PPAs — SPS has entered into PPAs with other utilities and energy suppliers for purchased power to meet system load and energy requirements, operating reserve obligations and as part of wholesale and commodity trading activities. In general, these agreements provide for energy payments, based on actual energy delivered and capacity payments. Certain PPAs, accounted for as executory contracts with various expiration dates through 2024, contain minimum energy purchase requirements. Included in electric fuel and purchased power expenses for PPAs accounted for as executory contracts, were payments for capacity of $12 million, $12 million and $20 million in 2021, 2020 and 2019, respectively. At Dec. 31, 2021, the estimated future payments for capacity that SPS is obligated to purchase pursuant to these executory contracts, subject to availability, were as follows: (Millions of Dollars) Capacity 2022 $ 12 2023 12 2024 6 2025 — 2026 — Thereafter — Total $ 30 Fuel Contracts — SPS has entered into various long-term commitments for the purchase and delivery of a significant portion of its coal and natural gas requirements. These contracts expire between 2022 and 2033. SPS is required to pay additional amounts depending on actual quantities shipped under these agreements. Estimated minimum purchases under these contracts as of Dec. 31, 2021: (Millions of Dollars) Coal Natural gas Natural gas 2022 $ 211 $ 44 $ 32 2023 50 — 29 2024 31 — 16 2025 — — 12 2026 — — 6 Thereafter — — 14 Total $ 292 $ 44 $ 109 VIEs PPAs — Under certain PPAs, SPS purchases power from IPPs for which SPS is required to reimburse fuel costs, or to participate in tolling arrangements under which SPS procures the natural gas required to produce the energy that it purchases. SPS has determined that certain IPPs are VIEs. SPS is not subject to risk of loss from the operations of these entities, and no significant financial support is required other than contractual payments for energy and capacity. In addition, certain solar PPAs provide an option to purchase emission allowances or sharing provisions related to production credits generated by the solar facility under contract. These specific PPAs create a variable interest in the IPP. SPS evaluated each of these VIEs for possible consolidation, including review of qualitative factors such as the length and terms of the contract, control over O&M, control over dispatch of electricity, historical and estimated future fuel and electricity prices, and financing activities. SPS concluded that these entities are not required to be consolidated in its financial statements because it does not have the power to direct the activities that most significantly impact the entities’ economic performance. SPS had approximately 1,197 MW of capacity under long-term PPAs at both Dec. 31, 2021 and 2020 with entities that have been determined to be VIEs. These agreements have expiration dates through 2041. Fuel Contracts — SPS purchases all of its coal requirements for its Harrington and Tolk plants from TUCO Inc. under contracts that will expire in December 2022. TUCO arranges for the purchase, receiving, transporting, unloading, handling, crushing, weighing, and delivery of coal to meet SPS’ requirements. TUCO is responsible for negotiating and administering contracts with coal suppliers, transporters and handlers. SPS has not provided any significant financial support to TUCO, other than contractual payments for delivered coal. However, the fuel contracts create a variable interest in TUCO due to SPS’ reimbursement of fuel procurement costs. SPS has determined that TUCO is a VIE. SPS has concluded that it is not the primary beneficiary of TUCO, because SPS does not have the power to direct the activities that most significantly impact TUCO’s economic performance.

State Audits (Details)

State Audits (Details)	Dec. 31, 2021USD ($)
Income Tax [Line Items]
state audits	$ 0

Unrealized Tax Benefits (Detail

Unrealized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2021	Jan. 01, 2020	Jan. 01, 2019
Income Tax [Line Items]
Unrecognized tax benefit — Permanent tax positions	$ 4	$ 3
Unrecognized tax benefit — Temporary tax positions	4	4
Balance at Dec. 31	8	7	$ 5	$ 7	$ 5	$ 5
Additions based on tax positions related to the current year	1	1	0
Additions for tax positions of prior years	0	5	0
Reductions for tax positions of prior years	0	4	0
NOL and tax credit carryforwards	(7)	(6)
Decrease in Unrecognized Tax Benefits is Reasonably Possible	5
(Payable) receivable for interest related to unrecognized tax benefits at Jan. 1	(1)	(1)	1	$ (1)	$ 1	$ 1
Interest expense related to unrecognized tax benefits	0	(2)	0
Unrecognized Tax Benefits, Income Tax Penalties Expense	$ 0	$ 0	$ 0

Other Income Tax Matters (Detai

Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2019
Income Tax [Line Items]
Federal NOL carryforward		$ 336	$ 0
Federal tax credit carryforwards		187	83
State NOL carryforwards		$ 111	$ 1
Federal statutory rate		21.00%	21.00%	[1]	21.00%	[1]
State income tax on pretax income, net of federal tax effect		2.50%	2.30%	[1]	2.20%	[1]
Wind PTCs		(39.70%)	(18.30%)	[1]	(7.90%)	[1]
Plant regulatory differences (b)	[2]	(4.80%)	(6.40%)	[1]	(5.00%)	[1]
Amortization of excess nonplant deferred taxes		(1.10%)	(0.80%)	[1]	(0.90%)	[1]
Change in unrecognized tax benefits		0.50%	0.30%	[1]	0.20%	[1]
Other, net		(1.20%)	(1.60%)	[1]	(0.60%)	[1]
Effective income tax rate		(22.80%)	(3.50%)	[1]	9.00%	[1]
Total income tax (benefit) expense		$ (59)	$ (10)		$ 26
Deferred tax (benefit) expense excluding items below		(23)	53		53
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(24)	(31)		(24)
Total deferred tax assets		(47)	22		29
Deferred fuel costs		34	(9)	[3]
Operating lease liabilities		464
NOL carryforward		76	0	[3]
income tax expense [Member]
Income Tax [Line Items]
Current federal tax benefit		(11)	(31)		(4)
Current state tax (benefit) expense		(1)	(1)		1
Current change in unrecognized tax expense		0	0		0
Deferred federal tax (benefit) expense		(57)	13		22
Deferred state tax expense		9	8		6
Deferred change in unrecognized tax expense		1	1		1
Total income tax (benefit) expense		(59)	(10)		$ 26
Net Deferred Tax Liablility [Member]
Income Tax [Line Items]
Federal tax credit carryforwards		187	83	[3]
Total deferred tax assets		478	307	[3]
Differences between book and tax bases of property		942	838	[3]
Operating lease assets		103	109	[3]
Regulatory assets		65	59	[3]
Pension expense		34	33	[3]
Other		2	2	[3]
Total deferred tax liabilities		1,180	1,032	[3]
Operating lease liabilities		103	109	[3]
Regulatory liabilities		98	104	[3]
Other employee benefits		7	7	[3]
Other		7	4	[3]
Net deferred tax liability		$ 702	$ 725	[3]
[1]	Prior periods have been reclassified 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.
[3]	Prior periods have been reclassified to conform to current year presentation.

Indeterminate AROs (Details)

Indeterminate AROs (Details) $ in Millions	Dec. 31, 2021USD ($)
Asset Retirement Obligations [Line Items]
Indeterminate Costs Incurred, Asset Retirement Obligation Due to Asbestos	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	General — SPS is engaged in the regulated generation, purchase, transmission, distribution and sale of electricity. SPS’ financial statements are presented in accordance with GAAP. All of SPS’ underlying accounting records also conform to the FERC uniform system of accounts or to systems required by various state regulatory commissions. Certain amounts in the financial statements or notes have been reclassified for comparative purposes; however, such reclassifications did not affect net income, total assets, liabilities, equity or cash flows. SPS has evaluated events occurring after Dec. 31, 2021 up to the date of issuance of these financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. Use of Estimates — SPS uses estimates based on the best information available in recording transactions and balances resulting from business operations. Estimates are used for items such as plant depreciable lives or potential disallowances, AROs, certain regulatory assets and liabilities, tax provisions, uncollectible amounts, environmental costs, unbilled revenues, jurisdictional fuel and energy cost allocations and actuarially determined benefit costs. Recorded estimates are revised when better information becomes available or actual amounts can be determined. Revisions can affect operating results. Regulatory Accounting — SPS accounts for income and expense items in accordance with accounting guidance for regulated operations. Under this guidance: • Certain costs, which would otherwise be charged to expense or other comprehensive income, are deferred as regulatory assets based on the expected ability to recover the costs in future rates. • Certain credits, which would otherwise be reflected as income or other comprehensive income, are deferred as regulatory liabilities based on the expectation the amounts will be returned to customers in future rates or because the amounts were collected in rates prior to the costs being incurred. Estimates of recovering deferred costs and returning deferred credits are based on specific ratemaking decisions or precedent for each item. Regulatory assets and liabilities are amortized consistent with the treatment in the rate setting process. If changes in the regulatory environment occur, SPS may no longer be eligible to apply this accounting treatment and may be required to eliminate regulatory assets and liabilities from its balance sheet. Such changes could have a material effect on SPS’ results of operations, financial condition and cash flows. See Note 4 for further information. Income Taxes — SPS accounts for income taxes using the asset and liability method, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. SPS defers income taxes for all temporary differences between pretax financial and taxable income and between the book and tax bases of assets and liabilities. SPS uses rates that are scheduled to be in effect when the temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the period that includes the enactment date. The effects of SPS’ tax rate changes are generally subject to a normalization method of accounting. Therefore, the revaluation of most of its net deferred taxes upon a tax rate reduction results in the establishment of a net regulatory liability, which would be refundable to utility customers over the remaining life of the related assets. SPS anticipates that a tax rate increase would result in the establishment of a regulatory asset, subject to an evaluation of whether future recovery is expected. Tax credits are recorded when earned unless there is a requirement to defer the benefit and amortize it over the book depreciable lives of the related property. The requirement to defer and amortize tax credits only applies to federal investment tax credits related to public utility property. Utility rate regulation also has resulted in the recognition of regulatory assets and liabilities related to income taxes. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. SPS follows the applicable accounting guidance to measure and disclose uncertain tax positions that it has taken or expects to take in its income tax returns. SPS recognizes a tax position in its financial statements when it is more likely than not that the position will be sustained upon examination based on the technical merits of the position. Recognition of changes in uncertain tax positions are reflected as a component of income tax expense. SPS reports interest and penalties related to income taxes within other (expense) income or interest charges in the statements of income. Xcel Energy Inc. and its subsidiaries, including SPS, file consolidated federal income tax returns as well as consolidated or separate state income tax returns. Federal income taxes paid by Xcel Energy Inc. are allocated to its subsidiaries based on separate company computations. A similar allocation is made for state income taxes paid by Xcel Energy Inc. in connection with consolidated state filings. Xcel Energy Inc. also allocates its own income tax benefits to its direct subsidiaries. See Note 7 for further information. Property, Plant and Equipment and Depreciation in Regulated Operations — Property, plant and equipment is stated at original cost. The cost of plant includes direct labor and materials, contracted work, overhead costs and AFUDC. The cost of plant retired is charged to accumulated depreciation and amortization. Amounts recovered in rates for future removal costs are recorded as regulatory liabilities. Significant additions or improvements extending asset lives are capitalized, while repairs and maintenance costs are charged to expense as incurred. Maintenance and replacement of items determined to be less than a unit of property are charged to operating expenses as incurred. Planned maintenance activities are charged to operating expense unless the cost represents the acquisition of an additional unit of property or the replacement of an existing unit of property. Property, plant and equipment is tested for impairment when it is determined that the carrying value of the assets may not be recoverable. A loss is recognized in the current period if it becomes probable that part of a cost of a plant under construction or recently completed plant will be disallowed for recovery from customers and a reasonable estimate of the disallowance can be made. For investments in property, plant and equipment that are abandoned and not expected to go into service, incurred costs and related deferred tax amounts are compared to the discounted estimated future rate recovery, and a loss is recognized, if necessary. SPS records depreciation expense using the straight-line method over the plant’s commission-approved useful life. Actuarial life studies are performed and submitted to the state and federal commissions for review. Upon acceptance by the various commissions, the resulting lives and net salvage rates are used to calculate depreciation. Plant removal costs are recovered in rates as authorized by the appropriate regulatory entities. The amount of removal costs is based on current factors used in existing depreciation rates. Depreciation expense, expressed as a percentage of average depreciable property, was 3.3% i n 2021, 3.1% in 2020 and 2.9% in 2019. See Note 3 for further information. AROs — SPS accounts for AROs under accounting guidance that requires a liability for the fair value of an ARO to be recognized in the period in which it is incurred if it can be reasonably estimated, with the offsetting associated asset retirement costs capitalized as a long-lived asset. The liability is generally increased over time by applying the effective interest method of accretion, and the capitalized costs are depreciated over the useful life of the long-lived asset. Changes resulting from revisions to the timing or amount of expected asset retirement cash flows are recognized as an increase or a decrease in the ARO. See Note 10 for further information. Benefit Plans and Other Postretirement Benefits — SPS maintains pension and postretirement benefit plans for eligible employees. Recognizing the cost of providing benefits and measuring the projected benefit obligation of these plans requires management to make various assumptions and estimates. Certain unrecognized actuarial gains and losses and unrecognized prior service costs or credits are deferred as regulatory assets and liabilities, rather than recorded as other comprehensive income, based on regulatory recovery mechanisms. See Note 9 for further information. Environmental Costs — Environmental costs are recorded when it is probable SPS is liable for remediation costs and the liability can be reasonably estimated. Costs are deferred as a regulatory asset if it is probable that the costs will be recovered from customers in future rates. Otherwise, the costs are expensed. For certain environmental costs related to facilities currently in use, such as for emission-control equipment, the cost is capitalized and depreciated over the life of the plant. Estimated remediation costs are regularly adjusted as estimates are revised and remediation proceeds. If other participating potentially responsible parties exist and acknowledge their potential involvement with a site, costs are estimated and recorded only for SPS’ expected share of the cost. Future costs of restoring sites are treated as a capitalized cost of plant retirement. The depreciation expense levels recoverable in rates include a provision for removal expenses. Removal costs recovered in rates before the related costs are incurred are classified as a regulatory liability. See Note 10 for further information. Revenue from Contracts with Customers — Performance obligations related to the sale of energy are satisfied as energy is delivered to customers. SPS recognizes revenue that corresponds to the price of the energy delivered to the customer. The measurement of energy sales to customers is generally based on the reading of their meters, which occurs systematically throughout the month. At the end of each month, amounts of energy delivered to customers since the date of the last meter reading are estimated and the corresponding unbilled revenue is recognized. SPS does not recognize a separate financing component of its collections from customers as contract terms are short-term in nature. SPS presents its revenues net of any excise or sales taxes or fees. SPS participates in SPP. SPS recognizes physical sales to customers (native load and wholesale) on a gross basis in electric revenues and cost of sales. Revenues and charges for short-term physical wholesale sales of excess energy transacted through RTOs are also recorded on a gross basis. Other revenues and charges settled/facilitated through an RTO are recorded on a net basis in cost of sales. See Note 6 for further information. Cash and Cash Equivalents — SPS considers investments in instruments with a remaining maturity of three months or less at the time of purchase to be cash equivalents. Accounts Receivable and Allowance for Bad Debts — Accounts receivable are stated at the actual billed amount net of an allowance for bad debts. SPS establishes an allowance for uncollectible receivables based on a policy that reflects its expected exposure to the credit risk of customers. As of Dec. 31, 2021 and 2020, the allowance for bad debts was $12 million and $8 million, respectively. Inventory — Inventory is recorded at average cost and consisted of the following: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Inventories Materials and supplies $ 29 $ 27 Fuel 22 9 Total inventories $ 51 $ 36 Fair Value Measurements — SPS presents cash equivalents, interest rate derivatives and commodity derivatives at estimated fair values in its financial statements. Cash equivalents are recorded at cost plus accrued interest; money market funds are measured using quoted NAVs. For interest rate derivatives, quoted prices based primarily on observable market interest rate curves are used to establish fair value. For commodity derivatives, the most observable inputs available are generally used to determine the fair value of each contract. In the absence of a quoted price, SPS may use quoted prices for similar contracts or internally prepared valuation models to determine fair value. For the pension and postretirement plan assets published trading data and pricing models, generally using the most observable inputs available, are utilized to estimate fair value for each security. See Notes 8 and 9 for further information. Derivative Instruments — SPS uses derivative instruments in connection with its utility commodity price and interest rate activities, including forward contracts, futures, swaps and options. Any derivative instruments not qualifying for the normal purchases and normal sales exception are recorded on the balance sheets at fair value as derivative instruments. Classification of changes in fair value for those derivative instruments is dependent on the designation of a qualifying hedging relationship. Changes in fair value of derivative instruments not designated in a qualifying hedging relationship are reflected in current earnings or as a regulatory asset or liability. Classification as a regulatory asset or liability is based on expected recovery of derivative instrument settlements through fuel and purchased energy cost recovery mechanisms. Interest rate hedging transactions are recorded as a component of interest expense. Normal Purchases and Normal Sales — SPS enters into contracts for purchases and sales of commodities for use in its operations. At inception, contracts are evaluated to determine whether a derivative exists and/or whether an instrument may be exempted from derivative accounting if designated as a normal purchase or normal sale. See Note 8 for further information. Other Utility Items AFUDC — AFUDC represents the cost of capital used to finance utility construction activity. AFUDC is computed by applying a composite financing rate to qualified CWIP. The amount of AFUDC capitalized as a utility construction cost is credited to other nonoperating income (for equity capital) and interest charges (for debt capital). AFUDC amounts capitalized are included in SPS’ rate base for establishing utility rates. Alternative Revenue — Certain rate rider mechanisms (including DSM programs) qualify as alternative revenue programs. These mechanisms arise from costs imposed upon the utility by action of a regulator or legislative body related to an environmental, public safety or other mandate or from other instances where the regulator authorizes a future surcharge in response to past activities or completed events. When certain criteria are met, including expected collection within 24 months, revenue is recognized equal to the revenue requirement, which may include incentives and return on rate base items. Billing amounts are revised periodically for differences between total amount collected and revenue earned, which may increase or decrease the level of revenue collected from customers. Alternative revenues arising from these programs are presented on a gross basis and disclosed separately from revenue from contracts with customers. See Note 6 for further information. Conservation Programs — SPS has implemented programs in its jurisdictions to assist customers in conserving energy and reducing peak demand on the electric system. These programs include commercial motor, air conditioner and lighting upgrades, as well as residential rebates for participation in air conditioner interruption and home weatherization. The costs incurred for some DSM programs are deferred as permitted by the applicable regulatory jurisdiction. For those programs, costs are deferred if it is probable future revenue will be provided to permit recovery of the incurred cost. Revenues recognized for incentive programs designed for recovery of lost margins and/or conservation performance incentives are limited to amounts expected to be collected within 24 months from the annual period in which they are earned. SPS recovers approved conservation program costs in base rate revenue or through a rider. Emission Allowances — Emission allowances are recorded at cost, including broker commission fees. The inventory accounting model is utilized for all emission allowances and sales of these allowances are included in electric revenues. RECs — Cost of RECs that are utilized for compliance is recorded as electric fuel and purchased power expense. SPS reduces recoverable fuel and purchased power costs for the cost of RECs received. An inventory accounting model is used to account for RECs recognized on the balance sheet, however these assets are classified as regulatory assets if amounts are recoverable in future rates. Sales of RECs are recorded in electric revenues on a gross basis. Cost of these RECs and amounts credited to customers under margin-sharing mechanisms are recorded in electric fuel and purchased power expense.

Property Plant and Equipment Pr

Property Plant and Equipment Property Plant and Equipment	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure	Major classes of property, plant and equipment (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Property, plant and equipment, net Electric plant $ 9,639 $ 9,229 Plant to be retired (a) 299 316 CWIP 171 146 Total property, plant and equipment 10,109 9,691 Less accumulated depreciation (2,271) (2,088) Property, plant and equipment, net $ 7,838 $ 7,603 (a) Includes expected retirement of Tolk and conversion of Harrington to natural gas.

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2021
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Regulatory assets and liabilities are created for amounts that regulators may allow to be collected or may require to be paid back to customers in future electric rates. SPS would be required to recognize the write-off of regulatory assets and liabilities in net income or other comprehensive income if changes in the utility industry no longer allow for the application of regulatory accounting guidance under GAAP. Components of regulatory assets: (Millions of Dollars) See Note(s) Remaining Amortization Period Dec. 31, 2021 Dec. 31, 2020 Regulatory Assets Current Noncurrent Current Noncurrent Pension and retiree medical obligations 9 Various $ 11 $ 135 $ 12 $ 178 Texas revenue surcharges One two 20 64 54 17 Excess deferred taxes — TCJA 7 Various 2 50 3 51 Recoverable deferred taxes on AFUDC Plant lives — 41 — 42 Net AROs (a) 1, 10 Various — 40 — 33 Losses on reacquired debt Term of related debt 1 19 1 20 Conservation programs (b) 1 One two 3 2 1 2 Deferred natural gas and electric energy/fuel costs One three 146 4 — — Other Various 10 25 5 14 Total regulatory assets $ 193 $ 380 $ 76 $ 357 (a) Includes amounts recorded for future recovery of AROs. (b) Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions. Components of regulatory liabilities: (Millions of Dollars) See Note(s) Remaining Amortization Period Dec. 31, 2021 Dec. 31, 2020 Regulatory Liabilities Current Noncurrent Current Noncurrent Deferred income tax adjustments and TCJA refunds (a) 7 Various $ 15 $ 486 $ 6 $ 513 Plant removal costs 1, 10 Various — 190 — 177 Revenue subject to refund One two 6 4 4 4 Gain from asset sales Various — 2 — 2 Deferred natural gas and electric energy/fuel costs Less than one year — — 35 — Contract valuation adjustments (b) 1, 8 One three 27 1 7 — Other Various 6 26 5 22 Total regulatory liabilities $ 54 $ 709 $ 57 $ 718 (a) Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA. (b) Includes the fair value of certain long-term PPAs used to meet energy capacity requirements.. At Dec. 31, 2021 and 2020, SPS’ regulatory assets not earning a return primarily included the unfunded portion of pension and retiree medical obligations and net AROs. In addition, SPS’ regulatory assets included $292 million and $114 million at Dec. 31, 2021 and 2020, respectively, of past expenditures not earning a return. Amounts are related to the Texas deferred fuel balance, losses on reacquired debt and certain rate case expenditures.

Borrowings and Other Financing

Borrowings and Other Financing Instruments	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	5. Borrowings and Other Financing Instruments Short-Term Borrowings SPS 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: (Millions of Dollars, Except Interest Rates) Three Months Ended Dec. 31, 2021 Year Ended Dec. 31 2021 2020 2019 Borrowing limit $ 100 $ 100 $ 100 $ 100 Amount outstanding at period end 91 91 — — Average amount outstanding 100 51 43 8 Maximum amount outstanding 100 100 100 100 Weighted average interest rate, computed on a daily basis 0.05 % 0.05 % 0.54 % 2.42 % Weighted average interest rate at end of period 0.05 0.05 N/A N/A Commercial Paper — Commercial paper outstanding: (Millions of Dollars, Except Interest Rates) Three Months Ended Dec. 31, 2021 Year Ended Dec. 31 2021 2020 2019 Borrowing limit $ 500 $ 500 $ 500 $ 400 Amount outstanding at period end 137 137 250 — Average amount outstanding 69 63 44 72 Maximum amount outstanding 137 342 250 316 Weighted average interest rate, computed on a daily basis 0.17 % 0.21 % 1.11 % 2.68 % Weighted average interest rate at end of period 0.26 0.26 0.29 N/A Letters of Credit — SPS may use letters of credit, typically with terms of one year, to provide financial guarantees for certain operating obligations. At both Dec. 31, 2021 and 2020, there were $2 million of letters of credit outstanding under the credit facility. The contract amounts of these letters of credit approximate their fair value and are subject to fees. Credit Facility — In order to use its commercial paper program to fulfill short-term funding needs, SPS 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 in an aggregate amount exceeding available capacity under this credit facility. The line of credit provides short-term financing in the form of notes payable to banks, letters of credit and back-up support for commercial paper borrowings. Features of SPS’ credit facility: Debt-to-Total Capitalization Ratio (a) Amount Facility May Be Increased (millions of dollars) Additional Periods for Which a One-Year Extension May Be Requested (b) 2021 2020 47% 48% $50 2 (a) The credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%. (b) All extension requests are subject to majority bank group approval. The credit facility has a cross-default provision that SPS would be in default on its borrowings under the facility if SPS or any of its future significant subsidiaries whose total assets exceed 15% of SPS’ total assets default on indebtedness in an aggregate principal amount exceeding $75 million. If SPS does not comply with the covenant, an event of default may be declared, and if not remedied, any outstanding amounts due under the facility can be declared due by the lender. As of Dec. 31, 2021, SPS was in compliance with all financial covenants. SPS had the following committed credit facility available as of Dec. 31, 2021 (in millions) of dollars: Credit Facility (a) Drawn (b) Available $500 $139 $361 (a) This credit facility matures in June 2024. (b) Includes letters of credit and outstanding commercial paper. All credit facility bank borrowings, outstanding letters of credit and outstanding commercial paper reduce the available capacity under the credit facility. SPS had no direct advances on the facility outstanding at Dec. 31, 2021 and 2020. Long-Term Borrowings and Other Financing Instruments Generally, all property of SPS is subject to the lien of its first mortgage indenture. Debt premiums, discounts and expenses are amortized over the life of the related debt. The premiums, discounts and expenses for refinanced debt are deferred and amortized over the life of the new issuance. Long-term debt obligations for SPS as of Dec. 31 (in millions of dollars): Financing Instrument Interest Rate Maturity Date 2021 2020 First mortgage bonds 3.30 % June 15, 2024 $ 150 $ 150 First mortgage bonds 3.30 June 15, 2024 200 200 Unsecured senior notes 6.00 Oct. 1, 2033 100 100 Unsecured senior notes 6.00 Oct. 1, 2036 250 250 First mortgage bonds 4.50 Aug. 15, 2041 200 200 First mortgage bonds 4.50 Aug. 15, 2041 100 100 First mortgage bonds 4.50 Aug. 15, 2041 100 100 First mortgage bonds 3.40 Aug. 15, 2046 300 300 First mortgage bonds 3.70 Aug. 15, 2047 450 450 First mortgage bonds 4.40 Nov. 15, 2048 300 300 First mortgage bonds 3.75 June 15, 2049 300 300 First mortgage bonds (b) 3.15 May 1, 2050 350 350 First mortgage bonds (a) 3.15 May 1, 2050 250 — Unamortized discount (9) (10) Unamortized debt issuance cost (28) (26) Total long-term debt $ 3,013 $ 2,764 (a) 2020 financing re-opened in 2021. (b) 2020 financing. Maturities of long-term debt: (Millions of Dollars) 2022 $ — 2023 — 2024 350 2025 — 2026 — Deferred Financing Costs — Deferred financing costs of approximately $28 million and $26 million, net of amortization, are presented as a deduction from the carrying amount of long-term debt at Dec. 31, 2021 and 2020, respectively. SPS is amortizing these financing costs over the remaining maturity periods of the related debt. Capital Stock — SPS has the following preferred stock: Preferred Stock Authorized (Shares) Par Value of Preferred Stock Preferred Stock Outstanding (Shares) 2021 and 2020 10,000,000 1.00 — Dividend Restrictions — SPS dividends are subject to the FERC’s jurisdiction, which prohibits the payment of dividends out of capital accounts. Dividends are solely to be paid from retained earnings. SPS is required to be current on particular interest payments before dividends can be paid. SPS’ state regulatory commissions additionally impose dividend limitations, which are more restrictive than those imposed by the FERC. Requirements and actuals as of Dec. 31, 2021: Equity to Total Capitalization Ratio Equity to Total Capitalization Ratio Actual (a) Low High 2021 45.0 % 55.0 % 54.5 % (a) Excludes short-term debt. Unrestricted Retained Earnings Total Capitalization Limit on Total Capitalization (a) $ 513 million $ 6,615 million N/A

Revenues

Revenues	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenues	Revenue is classified by the type of goods/services rendered and market/customer type. SPS’ operating revenues consisted of the following: Year Ended Dec. 31 (Millions of Dollars) 2021 2020 2019 Major revenue types Revenue from contracts with customers: Residential $ 375 $ 359 $ 352 C&I 842 739 800 Other 38 39 41 Total retail 1,255 1,137 1,193 Wholesale 873 345 361 Transmission 287 279 240 Other 6 4 3 Total revenue from contracts with customers 2,421 1,765 1,797 Alternative revenue and other 44 105 29 Total revenues $ 2,465 $ 1,870 $ 1,826

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
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 NAV. 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 forecasts of forward prices and volatilities on a valuation is evaluated, and may result in Level 3 classification. Electric commodity derivatives held by SPS include transmission congestion instruments, generally referred to as FTRs, purchased from SPP. FTRs purchased from an RTO are financial instruments that entitle or obligate the holder to monthly revenues or charges based on transmission congestion across a given transmission path. The value of an FTR is derived from, and designed to offset, the cost of transmission congestion. In addition to overall transmission load, congestion is also influenced by the operating schedules of power plants and the consumption of electricity pertinent to a given transmission path. Unplanned plant outages, scheduled plant maintenance, changes in the relative costs of fuels used in generation, weather and overall changes in demand for electricity can each impact the operating schedules of the power plants on the transmission grid and the value of an FTR. If forecasted costs of electric transmission congestion increase or decrease for a given FTR path, the value of that particular FTR instrument will likewise increase or decrease. Given the limited observability of important inputs to the value of FTRs between auction processes, including expected plant operating schedules and retail and wholesale demand, fair value measurements for FTRs have been assigned a Level 3. Non-trading monthly FTR settlements are expected to be recovered through fuel and purchased energy cost recovery mechanisms, and therefore changes in the fair value of the yet to be settled portions of FTRs are deferred as a regulatory asset or liability. Given this regulatory treatment and the limited magnitude of FTRs relative to the electric utility operations of SPS, the numerous unobservable quantitative inputs pertinent to the value of FTRs are immaterial to the financial statements of SPS. Derivative Instruments Fair Value Measurements SPS enters into derivative instruments, including forward contracts, for trading purposes and to manage risk in connection with changes in interest rates and electric utility commodity prices. Interest Rate Derivatives — SPS may enter into various instruments that effectively fix the interest payments on certain floating rate debt obligations or 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 Dec. 31, 2021, accumulated other comprehensive loss related to settled interest rate derivatives included immaterial net losses expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings. As of Dec. 31, 2021, SPS had no unsettled interest rate derivatives. Wholesale and Commodity Trading Risk — SPS conducts various wholesale and commodity trading activities, including the purchase and sale of electric capacity, energy and energy-related instruments, including derivatives. SPS is allowed to conduct these activities within guidelines and limitations as approved by its risk management committee, comprised of management personnel not directly involved in the activities governed by this policy. Commodity Derivatives — SPS enters into derivative instruments to manage variability of future cash flows from changes in commodity prices in its electric utility operations. This could include the purchase or sale of energy or energy-related products and FTRs. Gross notional amounts of FTRs: (Amounts in Millions) (a) Dec. 31, 2021 Dec. 31, 2020 MWh of electricity 8 5 (a) Amounts are not reflective of net positions in the underlying commodities. Consideration of Credit Risk and Concentrations — SPS 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 in the balance sheets. SPS’ most significant concentrations of credit risk with particular entities or industries are contracts with counterparties to its wholesale, trading and non-trading commodity activities. At Dec. 31, 2021, two of the eight most significant counterparties for these activities, comprising $8 million or 24% of this credit exposure, had investment grade ratings from S&P, Moody’s or Fitch Ratings. Five of the eight most significant counterparties, comprising $26 million or 76% of this credit exposure, were not rated by external rating agencies, but based on SPS’ internal analysis, had credit quality consistent with investment grade. One of these significant counterparties, comprising an immaterial amount or less than 1% of this credit exposure, had credit quality less than investment grade, based on internal analysis. Eight of these significant counterparties are municipal or cooperative electric entities, RTOs or other utilities. Impact of Derivative Activities on Income and Accumulated Other Comprehensive Loss — Changes in the fair value of FTRs resulting in a pre-tax net gain of $28 million and $7 million in Dec. 31, 2021 and 2019, respectively and $7 million in pre-tax net losses in the year ended Dec. 31, 2020, were reclassified as regulatory assets and liabilities. The classification as a regulatory asset or liability is based on expected recovery of FTR settlements through fuel and purchased energy cost recovery mechanisms. FTR settlement gains were $20 million and $6 million for the years ended Dec. 31, 2021 and 2019, respectively. For the year ended Dec. 31, 2020, FTR settlement losses were immaterial. Settlement gains and losses were recognized and recorded to electric fuel and purchased power. These derivative settlement gains and losses are shared with electric customers through fuel and purchased energy cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate. SPS had no derivative instruments designated as fair value hedges during the years ended Dec. 31, 2021, 2020 and 2019. Recurring Fair Value Measurements — SPS’ derivative assets and liabilities measured at fair value on a recurring basis were as follows: Dec. 31, 2021 Dec. 31, 2020 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative assets Other derivative instruments: Electric commodity $ — $ — $ 27 $ 27 $ — $ 27 $ — $ — $ 7 $ 7 $ — $ 7 Total current derivative assets $ — $ — $ 27 $ 27 $ — 27 $ — $ — $ 7 $ 7 $ — 7 PPAs (b) 3 3 Current derivative instruments $ 30 $ 10 Noncurrent derivative assets PPAs (b) $ 6 $ 9 Noncurrent derivative instruments $ 6 $ 9 Current derivative liabilities Other derivative instruments: PPAs (b) $ 4 $ 4 Current derivative instruments $ 4 $ 4 Noncurrent derivative liabilities PPAs (b) $ 6 $ 9 Noncurrent derivative instruments $ 6 $ 9 (a) SPS nets derivative instruments and related collateral on its 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 Dec. 31, 2021 and 2020. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no obligations to return cash collateral, respectively. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no rights to reclaim cash collateral, respectively. The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) During 2006, SPS qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities. Changes in Level 3 commodity derivatives for the years ended Dec. 31, 2021, 2020 and 2019: Year Ended Dec. 31 (Millions of Dollars) 2021 2020 2019 Balance at Jan. 1 $ 7 $ 12 $ 14 Purchases 10 23 27 Settlements (79) (23) (34) Net transactions recorded during the period: Net gains (losses) recognized as regulatory assets 89 (5) 5 Balance at Dec. 31 $ 27 $ 7 $ 12 SPS recognizes transfers between levels as of the beginning of each period. There were no transfers of amounts between levels for derivative instruments for Dec. 31, 2021, 2020 and 2019. Fair Value of Long-Term Debt As of Dec. 31, other financial instruments for which the carrying amount did not equal fair value: 2021 2020 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt $ 3,013 $ 3,454 $ 2,764 $ 3,381 Fair value of SPS’ 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 Dec. 31, 2021 and 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	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	9. Benefit Plans and Other Postretirement Benefits Pension and Postretirement Health Care Benefits Xcel Energy, which includes SPS, has several noncontributory, qualified, defined benefit pension plans that cover almost all employees. All newly hired or rehired employees participate under the Cash Balance formula, which is based on pay credits using a percentage of annual eligible pay and annual interest credits. The average annual interest crediting rates for these plans was 2.35, 2.37 and 3.12 percent in 2021, 2020, and 2019, respectively. Some employees may participate under legacy formulas such as the traditional final average pay or pension equity. Xcel Energy’s policy is to fully fund into an external trust the actuarially determined pension costs subject to the limitations of applicable employee benefit and tax laws. In addition to the qualified pension plans, Xcel Energy maintains a SERP and a nonqualified pension plan. The SERP is maintained for certain executives who participated in the plan in 2008, when the SERP was closed to new participants. The nonqualified pension plan provides benefits for compensation that is in excess of the limits applicable to the qualified pension plans, with distributions funded by Xcel Energy’s consolidated operating cash flows. Obligations of the SERP and nonqualified plan as of Dec. 31, 2021 and 2020 were $43 million and $43 million, respectively, of which $2 million was attributable to SPS in both years. In 2021 and 2020, Xcel Energy recognized net benefit cost for the SERP and nonqualified plans of $4 million and $6 million, respectively, of which immaterial amounts were attributable to SPS. Xcel Energy, which includes SPS, investment-return assumption considers the expected long-term performance for each of the asset classes in its pension and postretirement health care portfolio. Xcel Energy considers the historical returns achieved by its asset portfolios over long time periods, as well as long-term projected return levels. 20 years or longer period, as well as long-term projected return levels. Xcel Energy and SPS continually review pension assumptions. Pension cost determination assumes a forecasted mix of investment types over the long-term. • Investment returns in 2021 were above the assumed level of 6.39%. • Investment returns in 2020 were above the assumed level of 6.78%. • Investment returns in 2019 were above the assumed level of 6.78%. • In 2022, SPS’s expected investment-return assumption is 6.39%. Pension plan and postretirement benefit assets are invested in a portfolio according to Xcel Energy’s return, liquidity and diversification objectives to provide a source of funding for plan obligations and minimize contributions to the plan, within appropriate levels of risk. The principal mechanism for achieving these objectives is the asset allocation given the long-term risk, return, correlation and liquidity characteristics of each particular asset class. There were no significant concentrations of risk in any industry, index, or entity. Market volatility can impact even well-diversified portfolios and significantly affect the return levels achieved by the assets in any year. State agencies also have issued guidelines to the funding of postretirement benefit costs. SPS is required to fund postretirement benefit costs for Texas and New Mexico amounts collected in rates. These assets are invested in a manner consistent with the investment strategy for the pension plan. Xcel Energy’s ongoing investment strategy is based on plan-specific investment recommendations that seek to minimize potential investment and interest rate risk as a plan’s funded status increases over time. The investment recommendations consider many factors and generally result in a greater percentage of long-duration fixed income securities being allocated to specific plans having relatively higher funded status ratios and a greater percentage of growth assets being allocated to plans having relatively lower funded status ratios. Plan Assets For each of the fair value hierarchy levels, SPS’ pension plan assets measured at fair value: Dec. 31, 2021 (a) Dec. 31, 2020 (a) (Millions of Dollars) Level 1 Level 2 Level 3 Measured at NAV Total Level 1 Level 2 Level 3 Measured at NAV Total Cash equivalents $ 20 $ — $ — $ — $ 20 $ 31 $ — $ — $ — $ 31 Commingled funds 202 — — 169 371 211 — — 160 371 Debt securities — 148 1 — 149 — 110 1 — 111 Equity securities 10 — — — 10 11 — — — 11 Other — 2 — 5 7 2 1 — — 3 Total $ 232 $ 150 $ 1 $ 174 $ 557 $ 255 $ 111 $ 1 $ 160 $ 527 (a) See Note 8 for further information on fair value measurement inputs and methods. For each of the fair value hierarchy levels, SPS’ proportionate allocation of the total postretirement benefit plan assets that were measured at fair value: Dec. 31, 2021 (a) Dec. 31, 2020 (a) (Millions of Dollars) Level 1 Level 2 Level 3 Measured at NAV Total Level 1 Level 2 Level 3 Measured at NAV Total Cash equivalents $ 3 $ — $ — $ — $ 3 $ 3 $ — $ — $ — $ 3 Insurance contracts — 5 — — 5 — 5 — — 5 Commingled funds 6 — — 7 13 7 — — 7 14 Debt securities — 22 — — 22 — 22 — — 22 Total $ 9 $ 27 $ — $ 7 $ 43 $ 10 $ 27 $ — $ 7 $ 44 (a) See Note 8 for further information on fair value measurement inputs and methods. No assets were transferred in or out of Level 3 for 2021 or 2020. Funded Status — Benefit obligations for both pension and postretirement plans decreased from Dec. 31, 2020 to Dec. 31, 2021, due primarily to benefit payments and increases in discount rates used in actuarial valuations. Comparisons of the actuarially computed benefit obligation, changes in plan assets and funded status of the pension and postretirement health care plans for SPS are as follows: Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2021 2020 Change in Benefit Obligation: Obligation at Jan. 1 $ 562 $ 519 $ 38 $ 44 Service cost 11 10 1 1 Interest cost 15 18 1 1 Plan amendments — — — — Actuarial (gain) loss (13) 45 (3) (5) Plan participants’ contributions — — — 1 Benefit payments (30) (30) (3) (4) Obligation at Dec. 31 $ 545 $ 562 $ 34 $ 38 Change in Fair Value of Plan Assets: Fair value of plan assets at Jan. 1 $ 527 $ 458 $ 44 $ 44 Actual return on plan assets 46 84 1 3 Employer contributions 14 15 — — Plan participants’ contributions — — 1 1 Benefit payments (30) (30) (3) (4) Fair value of plan assets at Dec. 31 $ 557 $ 527 $ 43 $ 44 Funded status of plans at Dec. 31 $ 12 $ (35) $ 9 $ 6 Amounts recognized in the Balance Sheet at Dec. 31: Noncurrent assets 12 — 9 6 Noncurrent liabilities — (35) — — Net amounts recognized $ 12 $ (35) $ 9 $ 6 Pension Benefits Postretirement Benefits Significant Assumptions Used to Measure Benefit Obligations: 2021 2020 2021 2020 Discount rate for year-end valuation 3.08 % 2.71 % 3.09 % 2.65 % Expected average long-term increase in compensation level 3.75 % 3.75 % N/A N/A Mortality table Pri-2012 Pri-2012 Pri-2012 Pri-2012 Health care costs trend rate — initial: Pre-65 N/A N/A 5.30 % 5.50 % Health care costs trend rate — initial: Post-65 N/A N/A 4.90 % 5.00 % Ultimate trend assumption — initial: Pre-65 N/A N/A 4.50 % 4.50 % Ultimate trend assumption — initial: Post-65 N/A N/A 4.50 % 4.50 % Years until ultimate trend is reached N/A N/A 4 5 Accumulated benefit obligation for the pension plan was $506 million and $519 million as of Dec. 31, 2021 and 2020, respectively. Net Periodic Benefit Cost (Credit) — Net periodic benefit cost (credit), other than the service cost component, is included in other income (expense) in the statements of income. Components of net periodic benefit cost (credit) and amounts recognized in other comprehensive income and regulatory assets and liabilities: Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2019 2021 2020 2019 Service cost $ 11 $ 10 $ 9 $ 1 $ 1 $ 1 Interest cost 15 18 20 1 1 2 Expected return on plan assets (30) (29) (28) (2) (2) (2) Amortization of prior service credit — — — — — (1) Amortization of net loss 14 12 11 (1) — — Settlement charge (a) — — 2 — — — Net periodic pension cost 10 11 14 (1) — — Effects of regulation — 2 1 — — — Net benefit cost recognized for financial reporting $ 10 $ 13 $ 15 $ (1) $ — $ — Significant Assumptions Used to Measure Costs: Discount rate 2.71 % 3.49 % 4.31 % 2.65 % 3.47 % 4.32 % Expected average long-term increase in compensation level 3.75 3.75 3.75 — % — — Expected average long-term rate of return on assets 6.39 6.78 6.78 4.10 4.50 5.30 (a) A settlement charge is required when the amount of all 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 2019, as a result of lump-sum distributions during each plan year , SPS recorded a total pension settlement charge of $2 million. A total of $1 million of that amount was recorded in the income statement in 2019. T here were no settlement charges recorded to the qualified pension plans in 2021 or 2020. Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2021 2020 Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost: Net loss $ 143 $ 186 $ (19) $ (18) Prior service credit (1) (1) (1) (1) Total $ 142 $ 185 $ (20) $ (19) Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates: Current regulatory assets $ 11 $ 11 $ — $ — Noncurrent regulatory assets 131 174 — — Current regulatory liabilities — — (1) (1) Noncurrent regulatory liabilities — — (19) (18) Total $ 142 $ 185 $ (20) $ (19) Measurement date Dec. 31, 2021 Dec. 31, 2020 Dec. 31, 2021 Dec. 31, 2020 Cash Flows — Funding requirements can be impacted by changes to actuarial assumptions, actual asset levels and other calculations prescribed by the requirements of income tax and other pension-related regulations. Required contributions were made in 2019 - 2022 to meet minimum funding requirements. Total voluntary and required pension funding contributions across all four of Xcel Energy’s pension plans were as follows: • $50 million in January 2022, of which none was attributable to SPS. • $131 million in 2021, of which $15 million was attributable to SPS. • $150 million in 2020, of which $14 million was attributable to SPS. • $154 million in 2019, of which $18 million was attributable to SPS. For future years, Xcel Energy and SPS anticipate contributions will be made as necessary. The postretirement health care plans have no funding requirements other than fulfilling benefit payment obligations when claims are presented and approved. Additional cash funding requirements are prescribed by certain state and federal rate regulatory authorities. Xcel Energy’s voluntary postretirement funding contributions were as follows: • $9 million during 2022. • $15 million during 2021. • $11 million during 2020. • $15 million during 2019. • Amounts attributable to SPS were immaterial. Target asset allocations: Pension Benefits Postretirement Benefits 2021 2020 2021 2020 Domestic and international equity securities 33 % 35 % 15 % 15 % Long-duration fixed income securities 37 35 — — Short-to-intermediate fixed income securities 11 13 71 72 Alternative investments 17 15 8 9 Cash 2 2 6 4 Total 100 % 100 % 100 % 100 % The asset allocations above reflect target allocations approved in the calendar year to take effect in the subsequent year Plan Amendments — In 2020 and 2019, there were no significant plan amendments made which affected the benefit obligation. In 2021, Xcel Energy amended the Xcel Energy Pension Plan and Xcel Energy Inc. Nonbargaining Pension Plan (South) to reduce supplemental benefits for non-bargaining participants as well as to allow the transfer of a portion of non-qualified pension obligations into the qualified plans. Projected Benefit Payments SPS’ projected benefit payments: (Millions of Dollars) Projected Gross Projected Expected Net Projected 2022 $ 33 $ 3 $ — $ 3 2023 31 2 — 2 2024 31 2 — 2 2025 32 2 — 2 2026 31 2 — 2 2027-2031 153 11 — 11 Defined Contribution Plans Xcel Energy, which includes SPS, maintains 401(k) and other defined contribution plans that cover most employees. The expense to these plans for SPS was approximately $3 million in 2021, 2020 and 2019.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	11. Related Party Transactions Xcel Energy Services Inc. provides management, administrative and other services for the subsidiaries of Xcel Energy Inc., including SPS. The services are provided and billed to each subsidiary in accordance with service agreements executed by each subsidiary. SPS uses services provided by Xcel Energy Services Inc. whenever possible. Costs are charged directly to the subsidiary and are allocated if they cannot be directly assigned. Xcel Energy, Inc., NSP-Minnesota, NSP-Wisconsin, PSCo and SPS have established a utility money pool arrangement. See Note 5 for further information. Significant affiliate transactions among the companies and related parties for the years ended Dec. 31: (Millions of Dollars) 2021 2020 2019 Operating expenses: Other operating expenses — paid to Xcel Energy Services Inc. $ 209 $ 200 $ 192 Accounts receivable and payable with affiliates at Dec. 31 were: 2021 2020 (Millions of Dollars) Accounts Receivable Accounts Payable Accounts Receivable Accounts Payable NSP-Minnesota $ 2 $ — $ 3 $ — PSCo 7 — 6 — Other subsidiaries of Xcel Energy Inc. — 16 — 17 $ 9 $ 16 $ 9 $ 17

Summarized Quarterly Financial

Summarized Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2021
Quarterly Financial Information Disclosure [Abstract]
Summarized Quarterly Financial Data (Unaudited)	Quarter Ended (Millions of Dollars) March 31, 2021 June 30, 2021 Sept. 30, 2021 Dec. 31, 2021 Operating revenues $ 395 $ 423 $ 615 $ 437 Operating income 53 80 163 63 Net income 43 72 127 53 Quarter Ended (Millions of Dollars) March 31, 2020 June 30, 2020 Sept. 30, 2020 Dec. 31, 2020 Operating revenues $ 395 $ 423 $ 615 $ 437 Operating income 53 80 163 63 Net income 43 72 127 53

Schedule II, Valuation and Qual

Schedule II, Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II, Valuation and Qualifying Accounts	Southwestern Public Service Co. Valuation and Qualifying Accounts Years Ended Dec. 31 Allowance for bad debts (Millions of Dollars) 2021 2020 2019 Balance at Jan. 1 $ 8 $ 5 $ 6 Additions charged to costs and expenses 6 6 6 Additions charged to other accounts (a) 3 2 2 Deductions from reserves (b) (5) (5) (9) Balance at Dec. 31 $ 12 $ 8 $ 5 (a) Recovery of amounts previously written-off. (b) Deductions related primarily to bad debt write-offs.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Business and System of Accounts	General — SPS is engaged in the regulated generation, purchase, transmission, distribution and sale of electricity. SPS’ financial statements are presented in accordance with GAAP. All of SPS’ underlying accounting records also conform to the FERC uniform system of accounts or to systems required by various state regulatory commissions. Certain amounts in the financial statements or notes have been reclassified for comparative purposes; however, such reclassifications did not affect net income, total assets, liabilities, equity or cash flows.
Subsequent Events	SPS has evaluated events occurring after Dec. 31, 2021 up to the date of issuance of these financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation.
Use of Estimates	Use of Estimates — SPS uses estimates based on the best information available in recording transactions and balances resulting from business operations. Estimates are used for items such as plant depreciable lives or potential disallowances, AROs, certain regulatory assets and liabilities, tax provisions, uncollectible amounts, environmental costs, unbilled revenues, jurisdictional fuel and energy cost allocations and actuarially determined benefit costs. Recorded estimates are revised when better information becomes available or actual amounts can be determined. Revisions can affect operating results.
Regulatory Accounting	Regulatory Accounting — SPS accounts for income and expense items in accordance with accounting guidance for regulated operations. Under this guidance: • Certain costs, which would otherwise be charged to expense or other comprehensive income, are deferred as regulatory assets based on the expected ability to recover the costs in future rates. • Certain credits, which would otherwise be reflected as income or other comprehensive income, are deferred as regulatory liabilities based on the expectation the amounts will be returned to customers in future rates or because the amounts were collected in rates prior to the costs being incurred. Estimates of recovering deferred costs and returning deferred credits are based on specific ratemaking decisions or precedent for each item. Regulatory assets and liabilities are amortized consistent with the treatment in the rate setting process. If changes in the regulatory environment occur, SPS may no longer be eligible to apply this accounting treatment and may be required to eliminate regulatory assets and liabilities from its balance sheet. Such changes could have a material effect on SPS’ results of operations, financial condition and cash flows. See Note 4 for further information.
Income Taxes	Income Taxes — SPS accounts for income taxes using the asset and liability method, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. SPS defers income taxes for all temporary differences between pretax financial and taxable income and between the book and tax bases of assets and liabilities. SPS uses rates that are scheduled to be in effect when the temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the period that includes the enactment date. The effects of SPS’ tax rate changes are generally subject to a normalization method of accounting. Therefore, the revaluation of most of its net deferred taxes upon a tax rate reduction results in the establishment of a net regulatory liability, which would be refundable to utility customers over the remaining life of the related assets. SPS anticipates that a tax rate increase would result in the establishment of a regulatory asset, subject to an evaluation of whether future recovery is expected. Tax credits are recorded when earned unless there is a requirement to defer the benefit and amortize it over the book depreciable lives of the related property. The requirement to defer and amortize tax credits only applies to federal investment tax credits related to public utility property. Utility rate regulation also has resulted in the recognition of regulatory assets and liabilities related to income taxes. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. SPS follows the applicable accounting guidance to measure and disclose uncertain tax positions that it has taken or expects to take in its income tax returns. SPS recognizes a tax position in its financial statements when it is more likely than not that the position will be sustained upon examination based on the technical merits of the position. Recognition of changes in uncertain tax positions are reflected as a component of income tax expense. SPS reports interest and penalties related to income taxes within other (expense) income or interest charges in the statements of income. Xcel Energy Inc. and its subsidiaries, including SPS, file consolidated federal income tax returns as well as consolidated or separate state income tax returns. Federal income taxes paid by Xcel Energy Inc. are allocated to its subsidiaries based on separate company computations. A similar allocation is made for state income taxes paid by Xcel Energy Inc. in connection with consolidated state filings. Xcel Energy Inc. also allocates its own income tax benefits to its direct subsidiaries. See Note 7 for further information.
Property, Plant and Equipment and Depreciation	Property, Plant and Equipment and Depreciation in Regulated Operations — Property, plant and equipment is stated at original cost. The cost of plant includes direct labor and materials, contracted work, overhead costs and AFUDC. The cost of plant retired is charged to accumulated depreciation and amortization. Amounts recovered in rates for future removal costs are recorded as regulatory liabilities. Significant additions or improvements extending asset lives are capitalized, while repairs and maintenance costs are charged to expense as incurred. Maintenance and replacement of items determined to be less than a unit of property are charged to operating expenses as incurred. Planned maintenance activities are charged to operating expense unless the cost represents the acquisition of an additional unit of property or the replacement of an existing unit of property. Property, plant and equipment is tested for impairment when it is determined that the carrying value of the assets may not be recoverable. A loss is recognized in the current period if it becomes probable that part of a cost of a plant under construction or recently completed plant will be disallowed for recovery from customers and a reasonable estimate of the disallowance can be made. For investments in property, plant and equipment that are abandoned and not expected to go into service, incurred costs and related deferred tax amounts are compared to the discounted estimated future rate recovery, and a loss is recognized, if necessary. SPS records depreciation expense using the straight-line method over the plant’s commission-approved useful life. Actuarial life studies are performed and submitted to the state and federal commissions for review. Upon acceptance by the various commissions, the resulting lives and net salvage rates are used to calculate depreciation. Plant removal costs are recovered in rates as authorized by the appropriate regulatory entities. The amount of removal costs is based on current factors used in existing depreciation rates. Depreciation expense, expressed as a percentage of average depreciable property, was 3.3% i n 2021, 3.1% in 2020 and 2.9% in 2019. See Note 3 for further information.
Asset Retirement Obligations	AROs — SPS accounts for AROs under accounting guidance that requires a liability for the fair value of an ARO to be recognized in the period in which it is incurred if it can be reasonably estimated, with the offsetting associated asset retirement costs capitalized as a long-lived asset. The liability is generally increased over time by applying the effective interest method of accretion, and the capitalized costs are depreciated over the useful life of the long-lived asset. Changes resulting from revisions to the timing or amount of expected asset retirement cash flows are recognized as an increase or a decrease in the ARO. See Note 10 for further information.
Benefit Plans and Other Postretirement Benefits	Benefit Plans and Other Postretirement Benefits — SPS maintains pension and postretirement benefit plans for eligible employees. Recognizing the cost of providing benefits and measuring the projected benefit obligation of these plans requires management to make various assumptions and estimates. Certain unrecognized actuarial gains and losses and unrecognized prior service costs or credits are deferred as regulatory assets and liabilities, rather than recorded as other comprehensive income, based on regulatory recovery mechanisms. See Note 9 for further information.
Environmental Costs	Environmental Costs — Environmental costs are recorded when it is probable SPS is liable for remediation costs and the liability can be reasonably estimated. Costs are deferred as a regulatory asset if it is probable that the costs will be recovered from customers in future rates. Otherwise, the costs are expensed. For certain environmental costs related to facilities currently in use, such as for emission-control equipment, the cost is capitalized and depreciated over the life of the plant. Estimated remediation costs are regularly adjusted as estimates are revised and remediation proceeds. If other participating potentially responsible parties exist and acknowledge their potential involvement with a site, costs are estimated and recorded only for SPS’ expected share of the cost.
Revenue From Contracts With Customers	Revenue from Contracts with Customers — Performance obligations related to the sale of energy are satisfied as energy is delivered to customers. SPS recognizes revenue that corresponds to the price of the energy delivered to the customer. The measurement of energy sales to customers is generally based on the reading of their meters, which occurs systematically throughout the month. At the end of each month, amounts of energy delivered to customers since the date of the last meter reading are estimated and the corresponding unbilled revenue is recognized. SPS does not recognize a separate financing component of its collections from customers as contract terms are short-term in nature. SPS presents its revenues net of any excise or sales taxes or fees. SPS participates in SPP. SPS recognizes physical sales to customers (native load and wholesale) on a gross basis in electric revenues and cost of sales. Revenues and charges for short-term physical wholesale sales of excess energy transacted through RTOs are also recorded on a gross basis. Other revenues and charges settled/facilitated through an RTO are recorded on a net basis in cost of sales. See Note 6 for further information.
Cash and Cash Equivalents	Cash and Cash Equivalents — SPS considers investments in instruments with a remaining maturity of three months or less at the time of purchase to be cash equivalents.
Accounts Receivable and Allowance for Bad Debts	Accounts Receivable and Allowance for Bad Debts — Accounts receivable are stated at the actual billed amount net of an allowance for bad debts. SPS establishes an allowance for uncollectible receivables based on a policy that reflects its expected exposure to the credit risk of customers.
Inventory	Inventory — Inventory is recorded at average cost and consisted of the following: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Inventories Materials and supplies $ 29 $ 27 Fuel 22 9 Total inventories $ 51 $ 36
Fair Value Measurements	Fair Value Measurements — SPS presents cash equivalents, interest rate derivatives and commodity derivatives at estimated fair values in its financial statements. Cash equivalents are recorded at cost plus accrued interest; money market funds are measured using quoted NAVs. For interest rate derivatives, quoted prices based primarily on observable market interest rate curves are used to establish fair value. For commodity derivatives, the most observable inputs available are generally used to determine the fair value of each contract. In the absence of a quoted price, SPS may use quoted prices for similar contracts or internally prepared valuation models to determine fair value. For the pension and postretirement plan assets published trading data and pricing models, generally using the most observable inputs available, are utilized to estimate fair value for each security. See Notes 8 and 9 for further information.
Derivative Instruments	Derivative Instruments — SPS uses derivative instruments in connection with its utility commodity price and interest rate activities, including forward contracts, futures, swaps and options. Any derivative instruments not qualifying for the normal purchases and normal sales exception are recorded on the balance sheets at fair value as derivative instruments. Classification of changes in fair value for those derivative instruments is dependent on the designation of a qualifying hedging relationship. Changes in fair value of derivative instruments not designated in a qualifying hedging relationship are reflected in current earnings or as a regulatory asset or liability. Classification as a regulatory asset or liability is based on expected recovery of derivative instrument settlements through fuel and purchased energy cost recovery mechanisms. Interest rate hedging transactions are recorded as a component of interest expense. Normal Purchases and Normal Sales — SPS enters into contracts for purchases and sales of commodities for use in its operations. At inception, contracts are evaluated to determine whether a derivative exists and/or whether an instrument may be exempted from derivative accounting if designated as a normal purchase or normal sale. See Note 8 for further information.
AFUDC	AFUDC — AFUDC represents the cost of capital used to finance utility construction activity. AFUDC is computed by applying a composite financing rate to qualified CWIP. The amount of AFUDC capitalized as a utility construction cost is credited to other nonoperating income (for equity capital) and interest charges (for debt capital). AFUDC amounts capitalized are included in SPS’ rate base for establishing utility rates.
Alternative Revenue Programs	Alternative Revenue — Certain rate rider mechanisms (including DSM programs) qualify as alternative revenue programs. These mechanisms arise from costs imposed upon the utility by action of a regulator or legislative body related to an environmental, public safety or other mandate or from other instances where the regulator authorizes a future surcharge in response to past activities or completed events. When certain criteria are met, including expected collection within 24 months, revenue is recognized equal to the revenue requirement, which may include incentives and return on rate base items. Billing amounts are revised periodically for differences between total amount collected and revenue earned, which may increase or decrease the level of revenue collected from customers. Alternative revenues arising from these programs are presented on a gross basis and disclosed separately from revenue from contracts with customers. See Note 6 for further information. Conservation Programs — SPS has implemented programs in its jurisdictions to assist customers in conserving energy and reducing peak demand on the electric system. These programs include commercial motor, air conditioner and lighting upgrades, as well as residential rebates for participation in air conditioner interruption and home weatherization. The costs incurred for some DSM programs are deferred as permitted by the applicable regulatory jurisdiction. For those programs, costs are deferred if it is probable future revenue will be provided to permit recovery of the incurred cost. Revenues recognized for incentive programs designed for recovery of lost margins and/or conservation performance incentives are limited to amounts expected to be collected within 24 months from the annual period in which they are earned. SPS recovers approved conservation program costs in base rate revenue or through a rider.
Emission Allowances	Emission Allowances — Emission allowances are recorded at cost, including broker commission fees. The inventory accounting model is utilized for all emission allowances and sales of these allowances are included in electric revenues.
Renewable Energy Credits	RECs — Cost of RECs that are utilized for compliance is recorded as electric fuel and purchased power expense. SPS reduces recoverable fuel and purchased power costs for the cost of RECs received. An inventory accounting model is used to account for RECs recognized on the balance sheet, however these assets are classified as regulatory assets if amounts are recoverable in future rates.
Segment Reporting, Policy [Policy Text Block]	Segment Information — SPS has only one reportable segment. SPS is a wholly owned subsidiary of Xcel Energy Inc. and operates in the regulated electric utility industry providing wholesale and retail electric service in the states of Texas and New Mexico.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Inventory (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosure - Inventory [Abstract]
Schedule of Utility Inventory [Table Text Block]	Inventory — Inventory is recorded at average cost and consisted of the following: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Inventories Materials and supplies $ 29 $ 27 Fuel 22 9 Total inventories $ 51 $ 36

Property Plant and Equipment _2

Property Plant and Equipment Property Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment	Major classes of property, plant and equipment (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Property, plant and equipment, net Electric plant $ 9,639 $ 9,229 Plant to be retired (a) 299 316 CWIP 171 146 Total property, plant and equipment 10,109 9,691 Less accumulated depreciation (2,271) (2,088) Property, plant and equipment, net $ 7,838 $ 7,603 (a) Includes expected retirement of Tolk and conversion of Harrington to natural gas.

Regulatory Assets and Liabili_2

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	Components of regulatory assets: (Millions of Dollars) See Note(s) Remaining Amortization Period Dec. 31, 2021 Dec. 31, 2020 Regulatory Assets Current Noncurrent Current Noncurrent Pension and retiree medical obligations 9 Various $ 11 $ 135 $ 12 $ 178 Texas revenue surcharges One two 20 64 54 17 Excess deferred taxes — TCJA 7 Various 2 50 3 51 Recoverable deferred taxes on AFUDC Plant lives — 41 — 42 Net AROs (a) 1, 10 Various — 40 — 33 Losses on reacquired debt Term of related debt 1 19 1 20 Conservation programs (b) 1 One two 3 2 1 2 Deferred natural gas and electric energy/fuel costs One three 146 4 — — Other Various 10 25 5 14 Total regulatory assets $ 193 $ 380 $ 76 $ 357 (a) Includes amounts recorded for future recovery of AROs. (b) Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.
Regulatory Liabilities	Components of regulatory liabilities: (Millions of Dollars) See Note(s) Remaining Amortization Period Dec. 31, 2021 Dec. 31, 2020 Regulatory Liabilities Current Noncurrent Current Noncurrent Deferred income tax adjustments and TCJA refunds (a) 7 Various $ 15 $ 486 $ 6 $ 513 Plant removal costs 1, 10 Various — 190 — 177 Revenue subject to refund One two 6 4 4 4 Gain from asset sales Various — 2 — 2 Deferred natural gas and electric energy/fuel costs Less than one year — — 35 — Contract valuation adjustments (b) 1, 8 One three 27 1 7 — Other Various 6 26 5 22 Total regulatory liabilities $ 54 $ 709 $ 57 $ 718 (a) Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA. (b) Includes the fair value of certain long-term PPAs used to meet energy capacity requirements..

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Money Pool [Table Text Block]	Money pool borrowings: (Millions of Dollars, Except Interest Rates) Three Months Ended Dec. 31, 2021 Year Ended Dec. 31 2021 2020 2019 Borrowing limit $ 100 $ 100 $ 100 $ 100 Amount outstanding at period end 91 91 — — Average amount outstanding 100 51 43 8 Maximum amount outstanding 100 100 100 100 Weighted average interest rate, computed on a daily basis 0.05 % 0.05 % 0.54 % 2.42 % Weighted average interest rate at end of period 0.05 0.05 N/A N/A
Short-Term Borrowings	Commercial paper outstanding: (Millions of Dollars, Except Interest Rates) Three Months Ended Dec. 31, 2021 Year Ended Dec. 31 2021 2020 2019 Borrowing limit $ 500 $ 500 $ 500 $ 400 Amount outstanding at period end 137 137 250 — Average amount outstanding 69 63 44 72 Maximum amount outstanding 137 342 250 316 Weighted average interest rate, computed on a daily basis 0.17 % 0.21 % 1.11 % 2.68 % Weighted average interest rate at end of period 0.26 0.26 0.29 N/A
Schedule Of Debt To Total Capitalization Ratio [Table Text Block]	Features of SPS’ credit facility: Debt-to-Total Capitalization Ratio (a) Amount Facility May Be Increased (millions of dollars) Additional Periods for Which a One-Year Extension May Be Requested (b) 2021 2020 47% 48% $50 2 (a) The credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%.	[1],[2]
Credit Facilities	SPS had the following committed credit facility available as of Dec. 31, 2021 (in millions) of dollars: Credit Facility (a) Drawn (b) Available $500 $139 $361 (a) This credit facility matures in June 2024. (b) Includes letters of credit and outstanding commercial paper.	[3],[4]
Schedule of Long-term Debt Instruments [Table Text Block]	Long-term debt obligations for SPS as of Dec. 31 (in millions of dollars): Financing Instrument Interest Rate Maturity Date 2021 2020 First mortgage bonds 3.30 % June 15, 2024 $ 150 $ 150 First mortgage bonds 3.30 June 15, 2024 200 200 Unsecured senior notes 6.00 Oct. 1, 2033 100 100 Unsecured senior notes 6.00 Oct. 1, 2036 250 250 First mortgage bonds 4.50 Aug. 15, 2041 200 200 First mortgage bonds 4.50 Aug. 15, 2041 100 100 First mortgage bonds 4.50 Aug. 15, 2041 100 100 First mortgage bonds 3.40 Aug. 15, 2046 300 300 First mortgage bonds 3.70 Aug. 15, 2047 450 450 First mortgage bonds 4.40 Nov. 15, 2048 300 300 First mortgage bonds 3.75 June 15, 2049 300 300 First mortgage bonds (b) 3.15 May 1, 2050 350 350 First mortgage bonds (a) 3.15 May 1, 2050 250 — Unamortized discount (9) (10) Unamortized debt issuance cost (28) (26) Total long-term debt $ 3,013 $ 2,764 (a) 2020 financing re-opened in 2021. (b) 2020 financing.	[5],[6]
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of long-term debt: (Millions of Dollars) 2022 $ — 2023 — 2024 350 2025 — 2026 —
Schedule of Stock by Class [Table Text Block]	SPS has the following preferred stock: Preferred Stock Authorized (Shares) Par Value of Preferred Stock Preferred Stock Outstanding (Shares) 2021 and 2020 10,000,000 1.00 —
Dividend Payment Restrictions [Text Block]	Requirements and actuals as of Dec. 31, 2021: Equity to Total Capitalization Ratio Equity to Total Capitalization Ratio Actual (a) Low High 2021 45.0 % 55.0 % 54.5 % (a) Excludes short-term debt. Unrestricted Retained Earnings Total Capitalization Limit on Total Capitalization (a) $ 513 million $ 6,615 million N/A
[1]	All extension requests are subject to majority bank group approval.
[2]	The credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%.
[3]	Includes letters of credit and outstanding commercial paper.
[4]	This credit facility matures in June 2024.
[5]	2020 financing
[6]	2020 financing re-opened in 2021

Revenues (Tables)

Revenues (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	SPS’ operating revenues consisted of the following: Year Ended Dec. 31 (Millions of Dollars) 2021 2020 2019 Major revenue types Revenue from contracts with customers: Residential $ 375 $ 359 $ 352 C&I 842 739 800 Other 38 39 41 Total retail 1,255 1,137 1,193 Wholesale 873 345 361 Transmission 287 279 240 Other 6 4 3 Total revenue from contracts with customers 2,421 1,765 1,797 Alternative revenue and other 44 105 29 Total revenues $ 2,465 $ 1,870 $ 1,826

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Summary of Statute of Limitations Applicable to Open Tax Years	Tax Year(s) Expiration 2014 - 2016 December 2022 2018 September 2022
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 Unrecognized tax benefit — Permanent tax positions $ 4 $ 3 Unrecognized tax benefit — Temporary tax positions 4 4 Total unrecognized tax benefit $ 8 $ 7 Changes in unrecognized tax benefits: (Millions of Dollars) 2021 2020 2019 Balance at Jan. 1 $ 7 $ 5 $ 5 Additions based on tax positions related to the current year 1 1 — Additions for tax positions of prior years — 5 — Reductions for tax positions of prior years — (4) — Balance at Dec. 31 $ 8 $ 7 $ 5
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) Dec. 31, 2021 Dec. 31, 2020 NOL and tax credit carryforwards $ (7) $ (6)
Interest Payable related to Unrecognized Tax Benefits	Interest payable related to unrecognized tax benefits: (Millions of Dollars) 2021 2020 2019 (Payable) receivable for interest related to unrecognized tax benefits at Jan. 1 $ (1) $ 1 $ 1 Interest expense related to unrecognized tax benefits — (2) — (Payable) receivable for interest related to unrecognized tax benefits at Dec. 31 $ (1) $ (1) $ 1
NOL and Tax Credit Carryforwards	NOL amounts represent the tax loss that is carried forward and tax credits represent the deferred tax asset. NOL and tax credit carryforwards as of Dec. 31 were as follows: (Millions of Dollars) 2021 2020 Federal NOL carryforward $ 336 $ — Federal tax credit carryforwards 187 83 State NOL carryforwards 111 1
Schedule of Effective Income Tax Rate Reconciliation	Total income tax expense from operations differs from the amount computed by applying the statutory federal income tax rate to income before income tax expense. Effective income tax rate for years ended Dec. 31: 2021 2020 (a) 2019 (a) Federal statutory rate 21.0 % 21.0 % 21.0 % State income tax on pretax income, net of federal tax effect 2.5 2.3 2.2 Increases (decreases) in tax from: Wind PTCs (39.7) (18.3) (7.9) Plant regulatory differences (b) (4.8) (6.4) (5.0) Amortization of excess nonplant deferred taxes (1.1) (0.8) (0.9) Change in unrecognized tax benefits 0.5 0.3 0.2 Other, net (1.2) (1.6) (0.6) Effective income tax rate (22.8) % (3.5) % 9.0 % (a) Prior periods have been reclassified 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.
Schedule of Components of Income Tax Expense (Benefit)	Components of income tax expense for years ended Dec. 31: (Millions of Dollars) 2021 2020 2019 Current federal tax benefit $ (11) $ (31) $ (4) Current state tax (benefit) expense (1) (1) 1 Current change in unrecognized tax expense — — — Deferred federal tax (benefit) expense (57) 13 22 Deferred state tax expense 9 8 6 Deferred change in unrecognized tax expense 1 1 1 Total income tax (benefit) expense $ (59) $ (10) $ 26 Components of deferred income tax expense as of Dec. 31: (Millions of Dollars) 2021 2020 2019 Deferred tax (benefit) expense excluding items below $ (23) $ 53 $ 53 Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities (24) (31) (24) Deferred tax (benefit) expense $ (47) $ 22 $ 29
Schedule of Deferred Tax Assets and Liabilities	Components of the net deferred tax liability as of Dec. 31: (Millions of Dollars) 2021 2020 (a) Deferred tax liabilities: Differences between book and tax bases of property $ 942 $ 838 Operating lease assets 103 109 Regulatory assets 65 59 Deferred fuel costs 34 (9) Pension expense 34 33 Other 2 2 Total deferred tax liabilities $ 1,180 $ 1,032 Deferred tax assets: Operating lease liabilities $ 103 $ 109 Regulatory liabilities 98 104 Tax credit carryforward 187 83 NOL carryforward 76 — Other employee benefits 7 7 Other 7 4 Total deferred tax assets 478 307 Net deferred tax liability $ 702 $ 725 (a) Prior periods have been reclassified to conform to current year presentation.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Gross Notional Amounts of Commodity FTRs	(Amounts in Millions) (a) Dec. 31, 2021 Dec. 31, 2020 MWh of electricity 8 5 (a) Amounts are not reflective of net positions in the underlying commodities.
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	SPS’ derivative assets and liabilities measured at fair value on a recurring basis were as follows: Dec. 31, 2021 Dec. 31, 2020 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative assets Other derivative instruments: Electric commodity $ — $ — $ 27 $ 27 $ — $ 27 $ — $ — $ 7 $ 7 $ — $ 7 Total current derivative assets $ — $ — $ 27 $ 27 $ — 27 $ — $ — $ 7 $ 7 $ — 7 PPAs (b) 3 3 Current derivative instruments $ 30 $ 10 Noncurrent derivative assets PPAs (b) $ 6 $ 9 Noncurrent derivative instruments $ 6 $ 9 Current derivative liabilities Other derivative instruments: PPAs (b) $ 4 $ 4 Current derivative instruments $ 4 $ 4 Noncurrent derivative liabilities PPAs (b) $ 6 $ 9 Noncurrent derivative instruments $ 6 $ 9 (a) SPS nets derivative instruments and related collateral on its 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 Dec. 31, 2021 and 2020. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no obligations to return cash collateral, respectively. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no rights to reclaim cash collateral, respectively. The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) During 2006, SPS qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.
Changes in Level 3 Commodity Derivatives	Changes in Level 3 commodity derivatives for the years ended Dec. 31, 2021, 2020 and 2019: Year Ended Dec. 31 (Millions of Dollars) 2021 2020 2019 Balance at Jan. 1 $ 7 $ 12 $ 14 Purchases 10 23 27 Settlements (79) (23) (34) Net transactions recorded during the period: Net gains (losses) recognized as regulatory assets 89 (5) 5 Balance at Dec. 31 $ 27 $ 7 $ 12
Carrying Amount and Fair Value of Long-term Debt	2021 2020 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt $ 3,013 $ 3,454 $ 2,764 $ 3,381

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2021
Benefit Plans and Other Postretirement Benefits [Abstract]
Target Asset Allocations and Plan Assets Measured at Fair Value	For each of the fair value hierarchy levels, SPS’ pension plan assets measured at fair value: Dec. 31, 2021 (a) Dec. 31, 2020 (a) (Millions of Dollars) Level 1 Level 2 Level 3 Measured at NAV Total Level 1 Level 2 Level 3 Measured at NAV Total Cash equivalents $ 20 $ — $ — $ — $ 20 $ 31 $ — $ — $ — $ 31 Commingled funds 202 — — 169 371 211 — — 160 371 Debt securities — 148 1 — 149 — 110 1 — 111 Equity securities 10 — — — 10 11 — — — 11 Other — 2 — 5 7 2 1 — — 3 Total $ 232 $ 150 $ 1 $ 174 $ 557 $ 255 $ 111 $ 1 $ 160 $ 527 (a) See Note 8 for further information on fair value measurement inputs and methods. For each of the fair value hierarchy levels, SPS’ proportionate allocation of the total postretirement benefit plan assets that were measured at fair value: Dec. 31, 2021 (a) Dec. 31, 2020 (a) (Millions of Dollars) Level 1 Level 2 Level 3 Measured at NAV Total Level 1 Level 2 Level 3 Measured at NAV Total Cash equivalents $ 3 $ — $ — $ — $ 3 $ 3 $ — $ — $ — $ 3 Insurance contracts — 5 — — 5 — 5 — — 5 Commingled funds 6 — — 7 13 7 — — 7 14 Debt securities — 22 — — 22 — 22 — — 22 Total $ 9 $ 27 $ — $ 7 $ 43 $ 10 $ 27 $ — $ 7 $ 44 (a) See Note 8 for further information on fair value measurement inputs and methods. Target asset allocations: Pension Benefits Postretirement Benefits 2021 2020 2021 2020 Domestic and international equity securities 33 % 35 % 15 % 15 % Long-duration fixed income securities 37 35 — — Short-to-intermediate fixed income securities 11 13 71 72 Alternative investments 17 15 8 9 Cash 2 2 6 4 Total 100 % 100 % 100 % 100 %
Funded Status of Plans	Funded Status — Benefit obligations for both pension and postretirement plans decreased from Dec. 31, 2020 to Dec. 31, 2021, due primarily to benefit payments and increases in discount rates used in actuarial valuations. Comparisons of the actuarially computed benefit obligation, changes in plan assets and funded status of the pension and postretirement health care plans for SPS are as follows: Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2021 2020 Change in Benefit Obligation: Obligation at Jan. 1 $ 562 $ 519 $ 38 $ 44 Service cost 11 10 1 1 Interest cost 15 18 1 1 Plan amendments — — — — Actuarial (gain) loss (13) 45 (3) (5) Plan participants’ contributions — — — 1 Benefit payments (30) (30) (3) (4) Obligation at Dec. 31 $ 545 $ 562 $ 34 $ 38 Change in Fair Value of Plan Assets: Fair value of plan assets at Jan. 1 $ 527 $ 458 $ 44 $ 44 Actual return on plan assets 46 84 1 3 Employer contributions 14 15 — — Plan participants’ contributions — — 1 1 Benefit payments (30) (30) (3) (4) Fair value of plan assets at Dec. 31 $ 557 $ 527 $ 43 $ 44 Funded status of plans at Dec. 31 $ 12 $ (35) $ 9 $ 6 Amounts recognized in the Balance Sheet at Dec. 31: Noncurrent assets 12 — 9 6 Noncurrent liabilities — (35) — — Net amounts recognized $ 12 $ (35) $ 9 $ 6 Pension Benefits Postretirement Benefits Significant Assumptions Used to Measure Benefit Obligations: 2021 2020 2021 2020 Discount rate for year-end valuation 3.08 % 2.71 % 3.09 % 2.65 % Expected average long-term increase in compensation level 3.75 % 3.75 % N/A N/A Mortality table Pri-2012 Pri-2012 Pri-2012 Pri-2012 Health care costs trend rate — initial: Pre-65 N/A N/A 5.30 % 5.50 % Health care costs trend rate — initial: Post-65 N/A N/A 4.90 % 5.00 % Ultimate trend assumption — initial: Pre-65 N/A N/A 4.50 % 4.50 % Ultimate trend assumption — initial: Post-65 N/A N/A 4.50 % 4.50 % Years until ultimate trend is reached N/A N/A 4 5 Accumulated benefit obligation for the pension plan was $506 million and $519 million as of Dec. 31, 2021 and 2020, respectively. Net Periodic Benefit Cost (Credit) — Net periodic benefit cost (credit), other than the service cost component, is included in other income (expense) in the statements of income. Components of net periodic benefit cost (credit) and amounts recognized in other comprehensive income and regulatory assets and liabilities:
Components of Net Periodic Benefit Costs	Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2019 2021 2020 2019 Service cost $ 11 $ 10 $ 9 $ 1 $ 1 $ 1 Interest cost 15 18 20 1 1 2 Expected return on plan assets (30) (29) (28) (2) (2) (2) Amortization of prior service credit — — — — — (1) Amortization of net loss 14 12 11 (1) — — Settlement charge (a) — — 2 — — — Net periodic pension cost 10 11 14 (1) — — Effects of regulation — 2 1 — — — Net benefit cost recognized for financial reporting $ 10 $ 13 $ 15 $ (1) $ — $ — Significant Assumptions Used to Measure Costs: Discount rate 2.71 % 3.49 % 4.31 % 2.65 % 3.47 % 4.32 % Expected average long-term increase in compensation level 3.75 3.75 3.75 — % — — Expected average long-term rate of return on assets 6.39 6.78 6.78 4.10 4.50 5.30 (a) A settlement charge is required when the amount of all 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 2019, as a result of lump-sum distributions during each plan year , SPS recorded a total pension settlement charge of $2 million. A total of $1 million of that amount was recorded in the income statement in 2019. T
Projected Benefit Payments for the Pension and Postretirement Benefit Plans	Projected Benefit Payments SPS’ projected benefit payments: (Millions of Dollars) Projected Gross Projected Expected Net Projected 2022 $ 33 $ 3 $ — $ 3 2023 31 2 — 2 2024 31 2 — 2 2025 32 2 — 2 2026 31 2 — 2 2027-2031 153 11 — 11
Other Postretirement Benefits Plan [Member]
Benefit Plans and Other Postretirement Benefits [Abstract]
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost	Pension Benefits Postretirement Benefits (Millions of Dollars) 2021 2020 2021 2020 Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost: Net loss $ 143 $ 186 $ (19) $ (18) Prior service credit (1) (1) (1) (1) Total $ 142 $ 185 $ (20) $ (19) Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates: Current regulatory assets $ 11 $ 11 $ — $ — Noncurrent regulatory assets 131 174 — — Current regulatory liabilities — — (1) (1) Noncurrent regulatory liabilities — — (19) (18) Total $ 142 $ 185 $ (20) $ (19) Measurement date Dec. 31, 2021 Dec. 31, 2020 Dec. 31, 2021 Dec. 31, 2020

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Asset Retirement Obligations	SPS’ AROs were as follows: 2021 (Millions of Dollars) Jan. 1, 2021 Accretion Dec. 31, 2021 (a) Electric Steam and other production $ 52 $ 2 $ 54 Wind 50 2 52 Distribution 10 — 10 Total liability $ 112 $ 4 $ 116 (a) There were no ARO amounts incurred, settled or revised in 2021. 2020 (Millions of Jan. 1, 2020 Amounts Incurred (a) Amounts Settled (b) Accretion Dec. 31, 2020 (c) Electric Steam and other production $ 51 $ — $ (2) $ 3 $ 52 Wind 16 33 — 1 50 Distribution 10 — — — 10 Total liability $ 77 $ 33 $ (2) $ 4 $ 112 (a) Amounts incurred related to the Sagamore wind farm placed in service in 2020. (b) Amounts settled related to asbestos abatement projects. (c) No AROs were revised in 2020.
Assets and Liabilities, Lessee [Table Text Block]	Operating lease ROU assets: (Millions of Dollars) Dec. 31, 2021 Dec. 31, 2020 PPAs $ 500 $ 500 Other 45 50 Gross operating lease ROU assets 545 550 Accumulated amortization (82) (58) Net operating lease ROU assets $ 463 $ 492
Lease, Cost [Table Text Block]	Components of lease expense: (Millions of Dollars) 2021 2020 2019 Operating leases PPA capacity payments $ 53 $ 48 $ 48 Other operating leases (a) 4 3 5 Total operating lease expense (b) $ 57 $ 51 $ 53 (a) Includes short-term lease expense o f $1 million , $1 million and $2 million for 2021, 2020 and 2019, respectively.
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Commitments under operating leases as of Dec. 31, 2021: (Millions of Dollars) PPA (a) (b) Operating Leases Other Operating Leases Total Leases 2022 $ 46 $ 3 $ 49 2023 46 3 49 2024 46 3 49 2025 46 4 50 2026 46 4 50 Thereafter 312 40 352 Total minimum obligation 542 57 599 Interest component of obligation (120) (15) (135) Present value of minimum obligation 422 42 464 Less current portion (30) Noncurrent operating and finance lease liabilities $ 434 Weighted-average remaining lease term in years 12 (a) Amounts do not include PPAs accounted for as executory contracts and/or contingent payments, such as energy payments on renewable PPAs. (b) PPA operating leases contractually expire at various dates through 2033.
Estimated Future Payments for Capacity and Energy Pursuant to Purchased Power Agreements	At Dec. 31, 2021, the estimated future payments for capacity that SPS is obligated to purchase pursuant to these executory contracts, subject to availability, were as follows: (Millions of Dollars) Capacity 2022 $ 12 2023 12 2024 6 2025 — 2026 — Thereafter — Total $ 30
Estimated Minimum Purchases Under Fuel Contracts	Estimated minimum purchases under these contracts as of Dec. 31, 2021: (Millions of Dollars) Coal Natural gas Natural gas 2022 $ 211 $ 44 $ 32 2023 50 — 29 2024 31 — 16 2025 — — 12 2026 — — 6 Thereafter — — 14 Total $ 292 $ 44 $ 109

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Significant affiliate transactions among the companies and related parties for the years ended Dec. 31: (Millions of Dollars) 2021 2020 2019 Operating expenses: Other operating expenses — paid to Xcel Energy Services Inc. $ 209 $ 200 $ 192 Accounts receivable and payable with affiliates at Dec. 31 were: 2021 2020 (Millions of Dollars) Accounts Receivable Accounts Payable Accounts Receivable Accounts Payable NSP-Minnesota $ 2 $ — $ 3 $ — PSCo 7 — 6 — Other subsidiaries of Xcel Energy Inc. — 16 — 17 $ 9 $ 16 $ 9 $ 17

Summarized Quarterly Financia_2

Summarized Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2021
Quarterly Financial Information Disclosure [Abstract]
Summarized Quarterly Financial Data (Unaudited)	Quarter Ended (Millions of Dollars) March 31, 2021 June 30, 2021 Sept. 30, 2021 Dec. 31, 2021 Operating revenues $ 395 $ 423 $ 615 $ 437 Operating income 53 80 163 63 Net income 43 72 127 53 Quarter Ended (Millions of Dollars) March 31, 2020 June 30, 2020 Sept. 30, 2020 Dec. 31, 2020 Operating revenues $ 395 $ 423 $ 615 $ 437 Operating income 53 80 163 63 Net income 43 72 127 53

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense expressed as a percentage of average depreciable property	3.30%	3.10%	2.90%
Cash and Cash Equivalents [Abstract]
cash and cash equivalents	$ 3
Accounts and Financing Receivable, after Allowance for Credit Loss, Current and Noncurrent [Abstract]
Accounts Receivable, Allowance for Credit Loss, Current	12,000,000	$ 8,000,000
Alternative Revenue Programs [Abstract]
maximum number of months following end of annual period	24
Public Utilities, Inventory [Line Items]
Inventory	51,000,000	36,000,000
Supplies
Public Utilities, Inventory [Line Items]
Inventory	29,000,000	27,000,000
Fuel
Public Utilities, Inventory [Line Items]
Inventory	$ 22,000,000	$ 9,000,000

Property Plant and Equipment _3

Property Plant and Equipment Property Plant and Equipment (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment		$ 10,109	$ 9,691
Accumulated Depreciation		(2,271)	(2,088)
Property, plant and equipment, net		7,838	7,603
Electric plant
Property, Plant and Equipment [Line Items]
Property, plant and equipment		9,639	9,229
Plant to be Retired [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	[1]	299	316
CWIP
Property, Plant and Equipment [Line Items]
Property, plant and equipment		$ 171	$ 146
[1]	Includes expected retirement of Tolk and conversion of Harrington to natural gas.

Regulatory Assets and Liabili_3

Regulatory Assets and Liabilities, Regulatory Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 193	$ 76
Regulatory Asset, Noncurrent		380	357
Regulatory assets not currently earning a return		292	114
Pension and Retiree Medical Obligations
Regulatory Assets [Line Items]
Regulatory Asset, Current		11	12
Regulatory Asset, Noncurrent		135	178
Texas revenue surcharge [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Current		20	54
Regulatory Asset, Noncurrent		$ 64	17
Texas revenue surcharge [Member] | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Texas revenue surcharge [Member] | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Excess deferred taxes - TCJA
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 2	3
Regulatory Asset, Noncurrent		50	51
Recoverable Deferred Taxes on AFUDC Recorded in Plant
Regulatory Assets [Line Items]
Regulatory Asset, Current		0	0
Regulatory Asset, Noncurrent		41	42
Net AROs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[1]	0	0
Regulatory Asset, Noncurrent	[1]	40	33
Losses on Reacquired Debt
Regulatory Assets [Line Items]
Regulatory Asset, Current		1	1
Regulatory Asset, Noncurrent		19	20
Conservation Programs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[2]	3	1
Regulatory Asset, Noncurrent	[2]	$ 2	2
Conservation Programs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Conservation Programs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		2 years
Deferred Fuel Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 146	0
Regulatory Asset, Noncurrent		$ 4	0
Deferred Fuel Costs | Minimum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
Deferred Fuel Costs | Maximum [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		3 years
Other
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 10	5
Regulatory Asset, Noncurrent		$ 25	$ 14
[1]	Includes amounts recorded for future recovery of AROs.
[2]	Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.

Regulatory Assets and Liabili_4

Regulatory Assets and Liabilities, Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 54	$ 57
Regulatory Liability, Noncurrent		709	718
Deferred Income Tax Adjustments and TCJA Refunds
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	[1]	15	6
Regulatory Liability, Noncurrent	[1]	486	513
Plant Removal Costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		0	0
Regulatory Liability, Noncurrent		190	177
Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		6	4
Regulatory Liability, Noncurrent		$ 4	4
Revenue Subject to Refund | Minimum [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		1 year
Revenue Subject to Refund | Maximum [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		2 years
Gain From Asset Sales
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 0	0
Regulatory Liability, Noncurrent		2	2
Deferred Electric Energy Costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		0	35
Regulatory Liability, Noncurrent		0	0
Contract Valuation Adjustments
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	[2]	27	7
Regulatory Liability, Noncurrent	[2]	$ 1	0
Contract Valuation Adjustments | Minimum [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		1 year
Contract Valuation Adjustments | Maximum [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		3 years
Other
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 6	5
Regulatory Liability, Noncurrent		$ 26	$ 22
[1]	Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA.
[2]	Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.

Short-Term Borrowings (Details)

Short-Term Borrowings (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount outstanding at period end	$ 137	$ 137	$ 250
Money Pool
Short-term Debt [Line Items]
Borrowing limit	100	100	100	$ 100
Amount outstanding at period end	91	91	0	0
Average amount outstanding	100	51	43	8
Maximum amount outstanding	$ 100	$ 100	$ 100	$ 100
Weighted average interest rate, computed on a daily basis (percentage)	0.05%	0.05%	0.54%	2.42%
Line of Credit Facility, Interest Rate at Period End	0.05%	0.05%
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	$ 500	$ 500	$ 500	$ 400
Amount outstanding at period end	137	137	250	0
Average amount outstanding	69	63	44	72
Maximum amount outstanding	$ 137	$ 342	$ 250	$ 316
Weighted average interest rate, computed on a daily basis (percentage)	0.17%	0.21%	1.11%	2.68%
Weighted average interest rate at period end (percentage)	0.26%	0.26%	0.29%

Letters of Credit (Details)

Letters of Credit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 137	$ 250
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 2	$ 2
Letter of Credit
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Period	1 year

Credit Facility (Details)

Credit Facility (Details) - Credit Facility $ in Millions		12 Months Ended
		Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio	[1]	47.00%	48.00%
Line Of Credit Facility Maximum Amount Credit Facility May Be Increased		$ 50
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[2]	2
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Line Of Credit Facility Minimum Threshhold Percentage Of Subsidiary Assets To Consolidated Assets Required To Initiate Cross Default Provisions		15.00%
Line of Credit Facility, Minimum Amount of Indebtedness in Default to Initiate Cross Default Provisions		$ 75
Direct advances on the credit outstanding		0	$ 0
SPS [Member]
Line of Credit Facility [Line Items]
Credit facility	[3]	500
Drawn	[4]	139
Available		$ 361
[1]	The credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%.
[2]	All extension requests are subject to majority bank group approval.
[3]	This credit facility matures in June 2024.
[4]	Includes letters of credit and outstanding commercial paper.

Long-Term Borrowings (Details)

Long-Term Borrowings (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net		$ (9)	$ (10)
Unamortized Debt Issuance Expense		(28)	(26)
Long-term Debt, Excluding Current Maturities		3,013	2,764
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months		0
Long-term Debt, Maturities, Repayments of Principal in Year Two		0
Long-term Debt, Maturities, Repayments of Principal in Year Three		350
Long-term Debt, Maturities, Repayments of Principal in Year Four		0
Long-term Debt, Maturities, Repayments of Principal in Year Five		0
Deferred Finance Costs, Noncurrent, Net		$ 28	26
First Mortgage Bonds, Series due: | Series Due June 15, 2024 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		3.30%
Face Amount		$ 150	150
First Mortgage Bonds, Series due: | Series Due June 15, 2024 2 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		3.30%
Face Amount		$ 200	200
First Mortgage Bonds, Series due: | Series Due Aug. 15, 2041 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		4.50%
Face Amount		$ 200	200
First Mortgage Bonds, Series due: | Series Due Aug. 15, 2041 2 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		4.50%
Face Amount		$ 100	100
First Mortgage Bonds, Series due: | Series Due Aug. 15, 2041 3 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		4.50%
Face Amount		$ 100	100
First Mortgage Bonds, Series due: | Series Due August 15, 2046 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		3.40%
Face Amount		$ 300	300
First Mortgage Bonds, Series due: | Series Due August 15, 2047 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		3.70%
Face Amount		$ 450	450
First Mortgage Bonds, Series due: | Series Due Nov. 15, 2048 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		4.40%
Face Amount		$ 300	300
First Mortgage Bonds, Series due: | Series Due June 15, 2049 [Domain]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		3.75%
Face Amount		$ 300	300
First Mortgage Bonds, Series due: | Series due May 1, 2050 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)	[1]	3.15%
Face Amount	[1]	$ 350	350
First Mortgage Bonds, Series due: | Series due May 1, 2050 2
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)	[2]	3.15%
Face Amount	[2]	$ 250	0
Unsecured Debt [Member] | Senior C and D Due Oct. 1, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		6.00%
Face Amount		$ 100	100
Unsecured Debt [Member] | Senior F Due Oct. 1, 2036 [Member]
Debt Instrument [Line Items]
Interest Rate, Stated Percentage (in hundredths)		6.00%
Face Amount		$ 250	250
Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities		$ 3,013	$ 2,764
[1]	2020 financing
[2]	2020 financing re-opened in 2021

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments Preferred Stock (Details)	Dec. 31, 2021$ / sharesshares
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	10,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 1
Preferred Stock, Shares Outstanding	0

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments Dividend and Other Restrictions (Details) $ in Millions	Dec. 31, 2021USD ($)
Dividend and Other Restrictions [Abstract]
Equity to total capitalization ratio (excluding short-term debt), low end of range	45.00%
Equity to total capitalization ratio (excluding short-term debt), high end of range	55.00%
Equity to total capitalization ratio (excluding short-term debt)	54.50%	[1]
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 513
Capitalization, Short term debt, long term debt and equity	$ 6,615,000
[1]	Excludes short-term debt.

Revenues (Details)

Revenues (Details) - Regulated Electric - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retail
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	$ 1,255	$ 1,137	$ 1,193
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	375	359	352
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	842	739	800
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	38	39	41
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	873	345	361
Transmission
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	287	279	240
Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	6	4	3
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,421	1,765	1,797
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	44	105	29
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 2,465	$ 1,870	$ 1,826

Commodity Derivatives (Details)

Commodity Derivatives (Details) - MWh MWh in Millions		Dec. 31, 2021	Dec. 31, 2020
Electric Commodity [Member]
Derivative [Line Items]
Notional Amount	[1]	8	5
[1]	Amounts are not reflective of net positions in the underlying commodities.

Consideration of Credit Risk an

Consideration of Credit Risk and Concentrations (Details) - Credit Concentration Risk $ in Millions	Dec. 31, 2021USD ($)Counterparty
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure	8
Municipal or Cooperative Entities or Other Utilities
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure	8
External Credit Rating, Investment Grade
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure	2
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties | $	$ 8
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	24.00%
No Investment Grade Ratings from External Credit Rating Agencies
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure	5
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties | $	$ 26
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	76.00%
External Credit Rating, Non Investment Grade
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure	1
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	1.00%

Impact of Derivative Activities

Impact of Derivative Activities on Income and Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Fair Value Hedges, Net	$ 0	$ 0	$ 0
Electric Commodity Contract | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Instruments Gain (Loss) Reclassified To Regulatory Assets And Liabilities Net	28	$ 7	7
Pre-tax gains (losses) reclassified into income during the period from regulatory assets and (liabilities)	$ 20		$ 6

Recurring Fair Value Measuremen

Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Return Cash Collateral		$ 0	$ 0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Reclaim Cash Collateral		0	0
Commodity Contract [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period		7	12	$ 14
Purchases		10	23	27
Settlements		(79)	(23)	(34)
Gains (losses) recognized as regulatory assets		89	(5)	5
Balance at end of period		27	7	12
Transfers Between Levels, Net		0	0	$ 0
Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Net		30	10
Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Net		6	9
Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Net		4	4
Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Net		6	9
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		27	7
Netting	[1]	0	0
Derivative Asset, Net		27	7
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		27	7
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		27	7
Netting	[1]	0	0
Derivative Asset, Net		27	7
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract | 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 | Electric Commodity Contract | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		27	7
Fair Value, Measurements, Nonrecurring | Other Current Assets | Purchased Power Agreements
Derivatives, Fair Value [Line Items]
Derivative Asset, Net	[2]	3	3
Fair Value, Measurements, Nonrecurring | Other Noncurrent Assets | Purchased Power Agreements
Derivatives, Fair Value [Line Items]
Derivative Asset, Net	[2]	6	9
Fair Value, Measurements, Nonrecurring | Other Current Liabilities | Purchased Power Agreements
Derivatives, Fair Value [Line Items]
Derivative Liability, Net	[2]	4	4
Fair Value, Measurements, Nonrecurring | Other Noncurrent Liabilities | Purchased Power Agreements
Derivatives, Fair Value [Line Items]
Derivative Liability, Net	[2]	$ 6	$ 9
[1]	SPS nets derivative instruments and related collateral on its 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 Dec. 31, 2021 and 2020. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no obligations to return cash collateral, respectively. At Dec. 31, 2021 and 2020, derivative assets and liabilities include no rights to reclaim cash collateral, respectively. The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.
[2]	During 2006, SPS qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.

Fair Value of Long-Term Debt (D

Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term Debt, Gross	$ 3,013	$ 2,764
Long-term debt, Fair Value	$ 3,454	$ 3,381

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits, Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019	Jan. 01, 2021
Pension Plan [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets			$ 557	[1]	$ 527	[1]	$ 458	$ 527
Plan asset investments measured at net asset value	[1]		174		160
Total benefit obligation			545		562		519
Net benefit cost recognized for financial reporting			$ 10		$ 13		$ 15
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Minimum number of years historical weighted average annual returns are used to determine investment return assumptions			20 years
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets			6.39%		6.78%		6.78%
Pension Plan [Member] | Forecast [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets For Next Fiscal Year		6.39%
Pension Plan [Member] | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		$ 232		$ 255
Pension Plan [Member] | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		150		111
Pension Plan [Member] | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		1		1
Pension Plan [Member] | Cash equivalents
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		20		31
Plan asset investments measured at net asset value	[1]		0		0
Pension Plan [Member] | Cash equivalents | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		20		31
Pension Plan [Member] | Cash equivalents | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Cash equivalents | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Commingled funds
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		371		371
Plan asset investments measured at net asset value	[1]		169		160
Pension Plan [Member] | Commingled funds | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		202		211
Pension Plan [Member] | Commingled funds | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Commingled funds | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Debt securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		149		111
Plan asset investments measured at net asset value	[1]		0		0
Pension Plan [Member] | Debt securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Debt securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		148		110
Pension Plan [Member] | Debt securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		1		1
Pension Plan [Member] | Equity securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		10		11
Plan asset investments measured at net asset value	[1]		0		0
Pension Plan [Member] | Equity securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		10		11
Pension Plan [Member] | Equity securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Equity securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Pension Plan [Member] | Other Investments [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		7		3
Plan asset investments measured at net asset value	[1]		5		0
Pension Plan [Member] | Other Investments [Member] | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		2
Pension Plan [Member] | Other Investments [Member] | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		2		1
Pension Plan [Member] | Other Investments [Member] | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets			43	[1]	44	[1]	$ 44	$ 44
Plan asset investments measured at net asset value	[1]		7		7
Total benefit obligation			34		38		44
Net benefit cost recognized for financial reporting			$ (1)		$ 0		$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets			4.10%		4.50%		5.30%
Other Postretirement Benefits Plan [Member] | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		$ 9		$ 10
Other Postretirement Benefits Plan [Member] | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		27		27
Other Postretirement Benefits Plan [Member] | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		3		3
Plan asset investments measured at net asset value	[1]		0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		3		3
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		5		5
Plan asset investments measured at net asset value	[1]		0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		5		5
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Commingled funds
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		13		14
Plan asset investments measured at net asset value	[1]		7		7
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		6		7
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Debt securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		22		22
Plan asset investments measured at net asset value	[1]		0		0
Other Postretirement Benefits Plan [Member] | Debt securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Other Postretirement Benefits Plan [Member] | Debt securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		22		22
Other Postretirement Benefits Plan [Member] | Debt securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]		0		0
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Total benefit obligation			2		2
Net benefit cost recognized for financial reporting			4		6
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan | Parent Company [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Total benefit obligation			$ 43		$ 43
[1]	See Note 8 for further information on fair value measurement inputs and methods.

Benefit Plans and Other Postr_4

Benefit Plans and Other Postretirement Benefits, Pension Plan Benefit Obligations, Cash Flows and Benefit Costs (Details)		12 Months Ended
		Dec. 31, 2021USD ($)Plan		Dec. 31, 2020USD ($)		Dec. 31, 2019USD ($)
Defined Benefit Plan Disclosure [Line Items]
Operating and maintenance expenses		$ 271,000,000		$ 275,000,000		$ 285,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Liability, Defined Benefit Plan, Noncurrent		(8,000,000)		(42,000,000)
Significant Assumptions Used to Measure Costs [Abstract]
annual interest crediting rates		2.35		2.37		3.12
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Payment for Settlement				2,000,000
Accumulated Benefit Obligation at Dec. 31		506,000,000		519,000,000
Operating and maintenance expenses				1,000,000		1,000,000
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1		562,000,000		519,000,000
Service cost		11,000,000		10,000,000		9,000,000
Interest cost		15,000,000		18,000,000		20,000,000
Plan amendments		0		0
Actuarial loss		(13,000,000)		45,000,000
Benefit payments		(30,000,000)		(30,000,000)
Obligation at Dec. 31		545,000,000		562,000,000		519,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		527,000,000	[1]	458,000,000
Actual return on plan assets		46,000,000		84,000,000
Employer contributions		14,000,000		15,000,000
Benefit payments		(30,000,000)		(30,000,000)
Fair value of plan assets at Dec. 31		557,000,000	[1]	527,000,000	[1]	458,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status		12,000,000		(35,000,000)
Liability, Defined Benefit Plan, Noncurrent		0		(35,000,000)
Assets for Plan Benefits, Defined Benefit Plan		12,000,000		0
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss		143,000,000		186,000,000
Prior service credit		(1,000,000)		(1,000,000)
Total		142,000,000		185,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Current regulatory assets		11,000,000		11,000,000
Noncurrent regulatory assets		131,000,000		174,000,000
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities		0		0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities		0		0
Total		$ 142,000,000		$ 185,000,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)		3.08%		2.71%
Expected average long-term increase in compensation level (as a percent)		3.75%		3.75%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 11,000,000		$ 10,000,000		9,000,000
Interest cost		15,000,000		18,000,000		20,000,000
Expected return on plan assets		(30,000,000)		(29,000,000)		(28,000,000)
Amortization of prior service cost		0		0		0
Amortization of net loss		14,000,000		12,000,000		11,000,000
Net periodic pension cost		10,000,000		11,000,000		14,000,000
Net benefit cost recognized for financial reporting		$ 10,000,000		$ 13,000,000		$ 15,000,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)		2.71%		3.49%		4.31%
Expected average long-term increase in compensation level (as a percent)		3.75%		3.75%		3.75%
Expected average long-term rate of return on assets (as a percent)		6.39%		6.78%		6.78%
Plan participant's contributions		$ 0		$ 0
Plan participant's contributions		0		0
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		12,000,000		(35,000,000)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]	0		0		$ 2,000,000
Defined Benefit Plan, Costs Not Recognized Due To Regulation		0		2,000,000		1,000,000
Pension Plan [Member] | SPS [Member]
Cash Flows [Abstract]
Payment for Pension Benefits		15,000,000		14,000,000		18,000,000
Other Postretirement Benefits Plan [Member]
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1		38,000,000		44,000,000
Service cost		1,000,000		1,000,000		1,000,000
Interest cost		1,000,000		1,000,000		2,000,000
Plan amendments		0		0
Actuarial loss		(3,000,000)		(5,000,000)
Benefit payments		(3,000,000)		(4,000,000)
Obligation at Dec. 31		34,000,000		38,000,000		44,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		44,000,000	[1]	44,000,000
Actual return on plan assets		1,000,000		3,000,000
Employer contributions		0		0
Benefit payments		(3,000,000)		(4,000,000)
Fair value of plan assets at Dec. 31		43,000,000	[1]	44,000,000	[1]	44,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status		9,000,000		6,000,000
Liability, Defined Benefit Plan, Noncurrent		0		0
Assets for Plan Benefits, Defined Benefit Plan		9,000,000		6,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss		(19,000,000)		(18,000,000)
Prior service credit		(1,000,000)		(1,000,000)
Total		(20,000,000)		(19,000,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Current regulatory assets		0		0
Noncurrent regulatory assets		0		0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities		(1,000,000)		(1,000,000)
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities		(19,000,000)		(18,000,000)
Total		$ (20,000,000)		$ (19,000,000)
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)		3.09%		2.65%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 1,000,000		$ 1,000,000		1,000,000
Interest cost		1,000,000		1,000,000		2,000,000
Expected return on plan assets		(2,000,000)		(2,000,000)		(2,000,000)
Amortization of prior service cost		0		0		(1,000,000)
Amortization of net loss		(1,000,000)		0		0
Net periodic pension cost		(1,000,000)		0		0
Net benefit cost recognized for financial reporting		$ (1,000,000)		$ 0		$ 0
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)		2.65%		3.47%		4.32%
Expected average long-term increase in compensation level (as a percent)		0.00%		0.00%		0.00%
Expected average long-term rate of return on assets (as a percent)		4.10%		4.50%		5.30%
Plan participant's contributions		$ 0		$ 1,000,000
Plan participant's contributions		1,000,000		1,000,000
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position		$ 9,000,000		$ 6,000,000
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65		5.30%		5.50%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65		4.90%		5.00%
Ultimate health care trend assumption rate (as a percent)		4.50%		4.50%
Period until ultimate trend rate is reached (in years)		$ 4		$ 5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]	0		0		$ 0
Defined Benefit Plan, Costs Not Recognized Due To Regulation		$ 0		$ 0		$ 0
Parent Company [Member] | Pension Plan [Member]
Cash Flows [Abstract]
Number of pension plans to which contributions were made | Plan		4
[1]	See Note 8 for further information on fair value measurement inputs and methods.
[2]	A settlement charge is required when the amount of all 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 2019, as a result of lump-sum distributions during each plan year , SPS recorded a total pension settlement charge of $2 million. A total of $1 million of that amount was recorded in the income statement in 2019. T

Benefit Plans and Other Postr_5

Benefit Plans and Other Postretirement Benefits, Postretirement Health Care Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Postretirement Benefits Plan [Member]
Postretirement Health Care Benefits [Abstract]
Discount rate for year-end valuation (as a percent)	3.09%	2.65%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65	5.30%	5.50%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65	4.90%	5.00%
Ultimate health care trend assumption rate (as a percent)	4.50%	4.50%
Period until ultimate trend rate is reached (in years)	$ 4	$ 5
Total benefit obligation	$ 34,000,000	$ 38,000,000	$ 44,000,000
Target pension asset allocations (as a percent)	100.00%	100.00%
Other Postretirement Benefits Plan [Member] | Equity securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	15.00%	15.00%
Other Postretirement Benefits Plan [Member] | Long-Duration Fixed Income and Long-duration fixed income and interest rate swap securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	0.00%	0.00%
Other Postretirement Benefits Plan [Member] | Short-to-intermediate fixed income securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	71.00%	72.00%
Other Postretirement Benefits Plan [Member] | Alternative investments
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	8.00%	9.00%
Other Postretirement Benefits Plan [Member] | Cash
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	6.00%	4.00%
Pension Plan [Member]
Postretirement Health Care Benefits [Abstract]
Discount rate for year-end valuation (as a percent)	3.08%	2.71%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	3.75%	3.75%
Total benefit obligation	$ 545,000,000	$ 562,000,000	$ 519,000,000
Target pension asset allocations (as a percent)	100.00%	100.00%
Pension Plan [Member] | Equity securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	33.00%	35.00%
Pension Plan [Member] | Long-Duration Fixed Income and Long-duration fixed income and interest rate swap securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	37.00%	35.00%
Pension Plan [Member] | Short-to-intermediate fixed income securities
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	11.00%	13.00%
Pension Plan [Member] | Alternative investments
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	17.00%	15.00%
Pension Plan [Member] | Cash
Postretirement Health Care Benefits [Abstract]
Target pension asset allocations (as a percent)	2.00%	2.00%
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan
Postretirement Health Care Benefits [Abstract]
Total benefit obligation	$ 2,000,000	$ 2,000,000

Benefit Plans and Other Postr_6

Benefit Plans and Other Postretirement Benefits, Fair Value of Postretirement Benefit Plan Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019	Jan. 01, 2021
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Operating and maintenance expenses		$ 271		$ 275		$ 285
Other Postretirement Benefits Plan [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets		43	[1]	44	[1]	44	$ 44
Plan assets at net asset value	[1]	7		7
Other Postretirement Benefits Plan [Member] | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	9		10
Other Postretirement Benefits Plan [Member] | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	27		27
Other Postretirement Benefits Plan [Member] | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	3		3
Plan assets at net asset value	[1]	0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	3		3
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Cash equivalents | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Commingled funds
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	13		14
Plan assets at net asset value	[1]	7		7
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	6		7
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Commingled funds | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	5		5
Plan assets at net asset value	[1]	0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	5		5
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Debt securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	22		22
Plan assets at net asset value	[1]	0		0
Other Postretirement Benefits Plan [Member] | Debt securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Other Postretirement Benefits Plan [Member] | Debt securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	22		22
Other Postretirement Benefits Plan [Member] | Debt securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member]
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets		557	[1]	527	[1]	458	$ 527
Plan assets at net asset value	[1]	174		160
Defined Benefit Plan, Plan Assets, Payment for Settlement				2
Operating and maintenance expenses				1		$ 1
Pension Plan [Member] | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	232		255
Pension Plan [Member] | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	150		111
Pension Plan [Member] | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	1		1
Pension Plan [Member] | Cash equivalents
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	20		31
Plan assets at net asset value	[1]	0		0
Pension Plan [Member] | Cash equivalents | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	20		31
Pension Plan [Member] | Cash equivalents | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Cash equivalents | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Commingled funds
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	371		371
Plan assets at net asset value	[1]	169		160
Pension Plan [Member] | Commingled funds | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	202		211
Pension Plan [Member] | Commingled funds | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Commingled funds | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Debt securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	149		111
Plan assets at net asset value	[1]	0		0
Pension Plan [Member] | Debt securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Debt securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	148		110
Pension Plan [Member] | Debt securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	1		1
Pension Plan [Member] | Equity securities
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	10		11
Plan assets at net asset value	[1]	0		0
Pension Plan [Member] | Equity securities | Level 1
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	10		11
Pension Plan [Member] | Equity securities | Level 2
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	0		0
Pension Plan [Member] | Equity securities | Level 3
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]
Fair value of plan assets	[1]	$ 0		$ 0
[1]	See Note 8 for further information on fair value measurement inputs and methods.

Benefit Plans and Other Postr_7

Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($)		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Operating and maintenance expenses		$ 271,000,000		$ 275,000,000		$ 285,000,000
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan amendments		0		0
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1		38,000,000		44,000,000
Service cost		1,000,000		1,000,000		1,000,000
Interest cost		1,000,000		1,000,000		2,000,000
Plan participant's contributions		0		1,000,000
Actuarial loss		(3,000,000)		(5,000,000)
Benefit payments		(3,000,000)		(4,000,000)
Obligation at Dec. 31		34,000,000		38,000,000		44,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		44,000,000	[1]	44,000,000
Actual return on plan assets		1,000,000		3,000,000
Plan participant's contributions		1,000,000		1,000,000
Employer contributions		0		0
Benefit payments		(3,000,000)		(4,000,000)
Fair value of plan assets at Dec. 31		43,000,000	[1]	44,000,000	[1]	44,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status		9,000,000		6,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss		(19,000,000)		(18,000,000)
Prior service credit		(1,000,000)		(1,000,000)
Total		(20,000,000)		(19,000,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost (Credit) Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets		0		0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets		0		0
Current regulatory liabilities		(1,000,000)		(1,000,000)
Noncurrent regulatory liabilities		(19,000,000)		(18,000,000)
Total		$ (20,000,000)		$ (19,000,000)
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)		3.09%		2.65%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65		5.30%		5.50%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65		4.90%		5.00%
Ultimate health care trend assumption rate (as a percent)		4.50%		4.50%
Period until ultimate trend rate is reached (in years)		$ 4		$ 5
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1,000,000		1,000,000		1,000,000
Interest cost		1,000,000		1,000,000		2,000,000
Expected return on plan assets		(2,000,000)		(2,000,000)		(2,000,000)
Amortization of prior service cost		0		0		(1,000,000)
Amortization of net loss		(1,000,000)		0		0
Settlement charge (a)	[2]	0		0		0
Net periodic pension cost		(1,000,000)		0		0
Defined Benefit Plan, Costs Not Recognized Due To Regulation		0		0		0
Net benefit cost recognized for financial reporting		$ (1,000,000)		$ 0		$ 0
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)		2.65%		3.47%		4.32%
Expected average long-term increase in compensation level (as a percent)		0.00%		0.00%		0.00%
Expected average long-term rate of return on assets (as a percent)		4.10%		4.50%		5.30%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Payment for Settlement				$ 2,000,000
Plan amendments		$ 0		0
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1		562,000,000		519,000,000
Service cost		11,000,000		10,000,000		$ 9,000,000
Interest cost		15,000,000		18,000,000		20,000,000
Plan participant's contributions		0		0
Actuarial loss		(13,000,000)		45,000,000
Benefit payments		(30,000,000)		(30,000,000)
Obligation at Dec. 31		545,000,000		562,000,000		519,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		527,000,000	[1]	458,000,000
Actual return on plan assets		46,000,000		84,000,000
Plan participant's contributions		0		0
Employer contributions		14,000,000		15,000,000
Benefit payments		(30,000,000)		(30,000,000)
Fair value of plan assets at Dec. 31		557,000,000	[1]	527,000,000	[1]	458,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status		12,000,000		(35,000,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss		143,000,000		186,000,000
Prior service credit		(1,000,000)		(1,000,000)
Total		142,000,000		185,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost (Credit) Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets		11,000,000		11,000,000
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets		131,000,000		174,000,000
Current regulatory liabilities		0		0
Noncurrent regulatory liabilities		0		0
Total		$ 142,000,000		$ 185,000,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)		3.08%		2.71%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		3.75%		3.75%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 11,000,000		$ 10,000,000		9,000,000
Interest cost		15,000,000		18,000,000		20,000,000
Expected return on plan assets		(30,000,000)		(29,000,000)		(28,000,000)
Amortization of prior service cost		0		0		0
Amortization of net loss		14,000,000		12,000,000		11,000,000
Settlement charge (a)	[2]	0		0		(2,000,000)
Net periodic pension cost		10,000,000		11,000,000		14,000,000
Defined Benefit Plan, Costs Not Recognized Due To Regulation		0		(2,000,000)		(1,000,000)
Net benefit cost recognized for financial reporting		$ 10,000,000		13,000,000		15,000,000
Operating and maintenance expenses				$ 1,000,000		$ 1,000,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)		2.71%		3.49%		4.31%
Expected average long-term increase in compensation level (as a percent)		3.75%		3.75%		3.75%
Expected average long-term rate of return on assets (as a percent)		6.39%		6.78%		6.78%
[1]	See Note 8 for further information on fair value measurement inputs and methods.
[2]	A settlement charge is required when the amount of all 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 2019, as a result of lump-sum distributions during each plan year , SPS recorded a total pension settlement charge of $2 million. A total of $1 million of that amount was recorded in the income statement in 2019. T

Net Periodic Benefit Cost (Deta

Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Operating and maintenance expenses		$ 271	$ 275	$ 285
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		11	10	9
Interest cost		15	18	20
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		(30)	(29)	(28)
Amortization of prior service cost		0	0	0
Defined Benefit Plan, Amortization of Gain (Loss)		14	12	11
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[1]	0	0	2
Net periodic pension cost		10	11	14
Defined Benefit Plan, Costs Not Recognized Due To Regulation		0	2	1
Net benefit cost recognized for financial reporting		$ 10	$ 13	$ 15
Discount rate (as a percent)		2.71%	3.49%	4.31%
Expected average long-term increase in compensation level (as a percent)		3.75%	3.75%	3.75%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		6.39%	6.78%	6.78%
Defined Benefit Plan, Plan Assets, Payment for Settlement			$ 2
Operating and maintenance expenses			1	$ 1
Net loss		$ 143	186
Prior service credit		(1)	(1)
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Total		142	185
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets		11	11
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets		131	174
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities		0	0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities		0	0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		1	1	1
Interest cost		1	1	2
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		(2)	(2)	(2)
Amortization of prior service cost		0	0	(1)
Defined Benefit Plan, Amortization of Gain (Loss)		(1)	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[1]	0	0	0
Net periodic pension cost		(1)	0	0
Defined Benefit Plan, Costs Not Recognized Due To Regulation		0	0	0
Net benefit cost recognized for financial reporting		$ (1)	$ 0	$ 0
Discount rate (as a percent)		2.65%	3.47%	4.32%
Expected average long-term increase in compensation level (as a percent)		0.00%	0.00%	0.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		4.10%	4.50%	5.30%
Net loss		$ (19)	$ (18)
Prior service credit		(1)	(1)
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Total		(20)	(19)
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets		0	0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets		0	0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities		(1)	(1)
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities		$ (19)	$ (18)
[1]	A settlement charge is required when the amount of all 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 2019, as a result of lump-sum distributions during each plan year , SPS recorded a total pension settlement charge of $2 million. A total of $1 million of that amount was recorded in the income statement in 2019. T

Cash Flow (Details)

Cash Flow (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2022USD ($)	Dec. 31, 2021USD ($)Plan	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		100.00%	100.00%
Pension Plan [Member] | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		33.00%	35.00%
Pension Plan [Member] | Long-Duration Fixed Income and Long-duration fixed income and interest rate swap securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		37.00%	35.00%
Pension Plan [Member] | Short-to-intermediate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		11.00%	13.00%
Pension Plan [Member] | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		17.00%	15.00%
Pension Plan [Member] | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		2.00%	2.00%
Pension Plan [Member] | Xcel Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits		$ 131	$ 150	$ 154
Pension Plan [Member] | SPS [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits		15	14	18
Pension Plan [Member] | Subsequent Event | Xcel Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	$ 50
Defined Benefit Plan, Overfunded Plan [Member] | Xcel Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits		$ 15	$ 11	$ 15
Defined Benefit Plan, Overfunded Plan [Member] | Subsequent Event | Xcel Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	$ 9
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		100.00%	100.00%
Other Postretirement Benefits Plan [Member] | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		15.00%	15.00%
Other Postretirement Benefits Plan [Member] | Long-Duration Fixed Income and Long-duration fixed income and interest rate swap securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		0.00%	0.00%
Other Postretirement Benefits Plan [Member] | Short-to-intermediate fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		71.00%	72.00%
Other Postretirement Benefits Plan [Member] | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		8.00%	9.00%
Other Postretirement Benefits Plan [Member] | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target pension asset allocations (as a percent)		6.00%	4.00%
Parent Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan number of pension plans to which contributions were made | Plan		4

Plan Amendments (Details)

Plan Amendments (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
plan ammendments	$ 0	$ 0

Projected Benefit Payments (Det

Projected Benefit Payments (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Defined Contribution Plan, Administrative Expense		$ 3	$ 3	$ 3
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		506	519
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2022		33
2023		31
2024		31
2025		32
2026		31
2027-2031		153
Pension Plan [Member] | Xcel Energy [Member]
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Payment for Pension Benefits		131	150	154
Pension Plan [Member] | Xcel Energy [Member] | Subsequent Event
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Payment for Pension Benefits	$ 50
Pension Plan [Member] | SPS [Member]
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Payment for Pension Benefits		15	14	18
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2022		3
2023		2
2024		2
2025		2
2026		2
2027-2031		11
Expected Medicare Part D Subsidies [Abstract]
2022		0
2023		0
2024		0
2025		0
2026		0
2027-2031		0
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
2022		3
2023		2
2024		2
2025		2
2026		2
2027-2031		11
Defined Benefit Plan, Overfunded Plan [Member] | Xcel Energy [Member]
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Payment for Pension Benefits		$ 15	$ 11	$ 15
Defined Benefit Plan, Overfunded Plan [Member] | Xcel Energy [Member] | Subsequent Event
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
Payment for Pension Benefits	$ 9

Commitments and Contingencies S

Commitments and Contingencies SPP OATT Upgrade Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Southwest Power Pool (SPP) [Member] | SPP Open Access Transmission Tariff Upgrade Costs [Member] | SPS [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Billed Charges For Transmission Service Upgrades	$ 13

Commitment and Contingencies Wi

Commitment and Contingencies Wind Operating Commitments (Details)	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Wind operating commitments, minimum net capacity factor	48.00%
Long-term Contract for Purchase of Electric Power [Line Items]
Wind operating commitments, minimum net capacity factor	48.00%
Actual Wind Operating Commitments	48.40%

Commitment and Contingencies Co

Commitment and Contingencies Contract Termination (Details)	12 Months Ended
	Dec. 31, 2021USD ($)MW
Commitments and Contingencies Disclosure [Abstract]
Lubbock Power and Light contract length	$ 25
Megawatts, Lubbock Power and Light contract | MW	170
Loss Contingencies [Line Items]
Settlement Agreement Payment, Lubbock Power and Light Contract	$ 78,000,000
Lubbock Power and Light contract length	$ 25
Megawatts, Lubbock Power and Light contract | MW	170

Commitments and Contingencies E

Commitments and Contingencies Environmental Requirements - Air (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)area
Implementation of the National Ambient Air Quality Standard for sulfur dioxide [Member] | Harrington Units 1 and 2 [Member]
Loss Contingencies [Line Items]
Exception to areas near generating plants attaining the SO2 NAAQS | area	1
Number of years unclassifiable areas will be monitored	3 years
Capital Addition Purchase Commitments [Member] | Regional Haze Rules [Member] | Tolk Units 1 and 2 [Member]
Loss Contingencies [Line Items]
Liability for estimated cost to comply with regulation | $	$ 600

Commitments and Contingencies,

Commitments and Contingencies, Asset Retirement Obligations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		$ 112	[1]	$ 77
Amounts Incurred		0		33	[2]
Amounts Settled		0		(2)	[3]
Accretion		4		4
Ending balance		116	[4]	112	[1]
Cash flow revisions		0		0
Electric Plant Steam Production Asbestos
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		52	[1]	51
Amounts Incurred	[2]			0
Amounts Settled	[3]			(2)
Accretion		2		3
Ending balance		54	[4]	52	[1]
Electric Plant Wind Production [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		50	[1]	16
Amounts Incurred	[2]			33
Amounts Settled	[3]			0
Accretion		2		1
Ending balance		52	[4]	50	[1]
Electric Plant Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		10	[1]	10
Amounts Incurred	[2]			0
Amounts Settled	[3]			0
Accretion		0		0
Ending balance		$ 10	[4]	$ 10	[1]
[1]	No AROs were revised in 2020.
[2]	Amounts incurred related to the Sagamore wind farm placed in service in 2020.
[3]	Amounts settled related to asbestos abatement projects.
[4]	There were no ARO amounts incurred, settled or revised in 2021.

Commitments and Contingencies_2

Commitments and Contingencies, Leases (Details) - USD ($)		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Maximum Length - Short-Term Leases		12 months
Operating Lease, Weighted Average Discount Rate, Percent		4.40%
Short-term Lease, Cost		$ 1,000,000	$ 1,000,000	$ 2,000,000
Operating Lease, Assets and Liabilities, Lessee [Abstract]
Operating Lease, Right-of-Use Asset, Gross		545,000,000	550,000,000
Operating Lease, Right-of-Use Asset, Accumulated Depreciation		(82,000,000)	(58,000,000)
Operating lease right-of-use assets		463,000,000	492,000,000
Lease, Cost [Abstract]
Operating Lease, Cost	[1]	57,000,000	51,000,000	53,000,000
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022		49,000,000
2023		49,000,000
2024		49,000,000
2025		50,000,000
2026		50,000,000
Thereafter		352,000,000
Total minimum obligation		599,000,000
Interest component of obligation		(135,000,000)
Operating lease liabilities		464,000,000
Less current portion		(30,000,000)	(28,000,000)
Operating Lease, Liability, Noncurrent		434,000,000	463,000,000
Weighted Average Remaining lease term, operating		12
Property, Plant and Equipment, Other Types [Member]
Operating Lease, Assets and Liabilities, Lessee [Abstract]
Operating Lease, Right-of-Use Asset, Gross		45,000,000	50,000,000
Lease, Cost [Abstract]
Operating Lease, Cost	[2]	4,000,000	3,000,000	5,000,000
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022		3,000,000
2023		3,000,000
2024		3,000,000
2025		4,000,000
2026		4,000,000
Thereafter		40,000,000
Total minimum obligation		57,000,000
Interest component of obligation		(15,000,000)
Operating lease liabilities		42,000,000
Purchased Power Agreements
Operating Lease, Assets and Liabilities, Lessee [Abstract]
Operating Lease, Right-of-Use Asset, Gross		500,000,000	500,000,000
Lease, Cost [Abstract]
Operating Lease, Cost		53,000,000	$ 48,000,000	$ 48,000,000
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022	[3],[4]	46,000,000
2023	[3],[4]	46,000,000
2024	[3],[4]	46,000,000
2025	[3],[4]	46,000,000
2026	[3],[4]	46,000,000
Thereafter	[3],[4]	312,000,000
Total minimum obligation	[3],[4]	542,000,000
Interest component of obligation	[3],[4]	(120,000,000)
Operating lease liabilities	[3],[4]	$ 422,000,000
[1]	PPA capacity payments are included in electric fuel and purchased power on the statements of income. Expense for other operating leases is included in O&M expense.
[2]	Includes short-term lease expense o f $1 million , $1 million and $2 million for 2021, 2020 and 2019, respectively.
[3]	Amounts do not include PPAs accounted for as executory contracts and/or contingent payments, such as energy payments on renewable PPAs.
[4]	PPA operating leases contractually expire at various dates through 2033.

Commitments and Contingencies_3

Commitments and Contingencies, Purchased Power Agreements (Details) - Capacity - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Purchased Power Agreements (PPAs) [Abstract]
Payments for capacity	$ 12	$ 12	$ 20
Estimated Future Payments Under PPAs [Abstract]
2022	12
2023	12
2024	6
2025	0
2026	0
Thereafter	0
Total	$ 30

Commitments and Contingencies_4

Commitments and Contingencies, Fuel Contracts (Details) $ in Millions	Dec. 31, 2021USD ($)
Coal
Fuel Contracts [Abstract]
2022	$ 211
2023	50
2024	31
2025	0
2026	0
Thereafter	0
Total	292
Natural Gas Supply [Member]
Fuel Contracts [Abstract]
2022	44
2023	0
2024	0
2025	0
2026	0
Thereafter	0
Total	44
Natural Gas Storage and Transportation [Member]
Fuel Contracts [Abstract]
2022	32
2023	29
2024	16
2025	12
2026	6
Thereafter	14
Total	$ 109

Commitments and Contingencies_5

Commitments and Contingencies, Variable Interest Entities (Details) - MW	Dec. 31, 2021	Dec. 31, 2020
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Purchased Power Agreements [Abstract]
Generating capacity (in MW)	1,197	1,197

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	$ 9	$ 9
Accounts payable	16	17
NSP-Minnesota
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	2	3
Accounts payable	0	0
PSCo
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	7	6
Accounts payable	0	0
Other Subsidiaries of Xcel Energy Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	16	17
Other Expense [Member]
Operating expenses [Abstract]
Costs and Expenses, Related Party	$ 209	$ 200	$ 192

Summarized Quarterly Financia_3

Summarized Quarterly Financial Data (Unaudited) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Regulated and Unregulated Operating Revenue	$ 437	$ 615	$ 423	$ 395	$ 437	$ 615	$ 423	$ 395
Operating income	63	163	80	53	63	163	80	53	$ 366	$ 359	$ 347
Net Income (Loss) Attributable to Parent	$ 53	$ 127	$ 72	$ 43	$ 53	$ 127	$ 72	$ 43	$ 318	$ 295	$ 263

Schedule II, Valuation and Qu_2

Schedule II, Valuation and Qualifying Accounts (Details) - Allowance for Bad Debts - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1		$ 8	$ 5	$ 6
Charged to costs and expenses		6	6	6
Charged to other accounts	[1]	3	2	2
Deductions from reserves	[2]	(5)	(5)	(9)
Balance at Dec. 31		$ 12	$ 8	$ 5
[1]	Recovery of amounts previously written-off.
[2]	Deductions related primarily to bad debt write-offs