Southwestern Public Service 10-Q 31 Jul 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Entity Registrant Name	SOUTHWESTERN PUBLIC SERVICE CO
Entity Central Index Key	0000092521
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-3034
Entity Tax Identification Number	75-0575400
Entity Incorporation, State or Country Code	NM
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		100

Management's Opinion

Management's Opinion	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Opinion	In the opinion of management, the accompanying unaudited financial statements contain all adjustments necessary to present fairly, in accordance with U.S. GAAP, the financial position of SPS as of June 30, 2020 and Dec. 31, 2019; the results of its operations, including the components of net income and comprehensive income, and changes in stockholder’s equity for the three and six months ended June 30, 2020 and 2019; and its cash flows for the six months ended June 30, 2020 and 2019. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after June 30, 2020 up to the date of issuance of these financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. The Dec. 31, 2019 balance sheet information has been derived from the audited 2019 financial statements included in the SPS Annual Report on Form 10-K for the year ended Dec. 31, 2019. These notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP on an annual basis have been condensed or omitted pursuant to such rules and regulations. For further information, refer to the financial statements and notes thereto, included in the SPS Annual Report on Form 10-K for the year ended Dec. 31, 2019, filed with the SEC on Feb. 21, 2020. Due to the seasonality of SPS’ electric sales, interim results are not necessarily an appropriate base from which to project annual results.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	The significant accounting policies set forth in Note 1 to the financial statements in the SPS Annual Report on Form 10-K for the year ended Dec. 31, 2019, appropriately represent, in all material respects, the current status of accounting policies and are incorporated herein by reference.

Accounting Pronouncements

Accounting Pronouncements	6 Months Ended
	Jun. 30, 2020
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.

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018		100
Beginning balance at Dec. 31, 2018	$ 2,536.6	$ 0	$ 1,932.3	$ 605.7	$ (1.4)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss) Attributable to Parent	112.9			112.9
Other comprehensive income	0.1				0.1
Dividends declared to parent	(140.9)			(140.9)
Contributions of capital by parent	375		375
Ending balance (in shares) at Jun. 30, 2019		100
Ending balance at Jun. 30, 2019	2,883.7	$ 0	2,307.3	577.7	(1.3)
Beginning balance (in shares) at Mar. 31, 2019		100
Beginning balance at Mar. 31, 2019	2,533.2	$ 0	1,932.3	602.3	(1.4)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss) Attributable to Parent	58.8			58.8
Other comprehensive income	0.1				0.1
Dividends declared to parent	(83.4)			(83.4)
Contributions of capital by parent	375		375
Ending balance (in shares) at Jun. 30, 2019		100
Ending balance at Jun. 30, 2019	$ 2,883.7	$ 0	2,307.3	577.7	(1.3)
Beginning balance (in shares) at Dec. 31, 2019	100	100
Beginning balance at Dec. 31, 2019	$ 2,884.5	$ 0	2,350.9	535	(1.4)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss) Attributable to Parent	114.4			114.4
Other comprehensive income	0.1				0.1
Dividends declared to parent	(130.2)			(130.2)
Contributions of capital by parent	$ 436		436
Ending balance (in shares) at Jun. 30, 2020	100	100
Ending balance at Jun. 30, 2020	$ 3,304.7	$ 0	2,786.9	519.1	(1.3)
Increase (Decrease) in Stockholders' Equity
Credit Losses, Topic 326 (ASC Topic 326)	(0.1)			(0.1)
Beginning balance (in shares) at Mar. 31, 2020		100
Beginning balance at Mar. 31, 2020	2,883.5	$ 0	2,382.9	502	(1.4)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss) Attributable to Parent	71.7			71.7
Other comprehensive income	0.1				0.1
Dividends declared to parent	(54.6)			(54.6)
Contributions of capital by parent	$ 404		404
Ending balance (in shares) at Jun. 30, 2020	100	100
Ending balance at Jun. 30, 2020	$ 3,304.7	$ 0	$ 2,786.9	$ 519.1	$ (1.3)

STATEMENTS OF INCOME (UNAUDITED

STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues
Operating revenues	$ 423.4	$ 410.5	$ 818.4	$ 864.6
Operating expenses
Electric fuel and purchased power	198.8	179.9	386.6	410.8
Operating and maintenance expenses	58.3	70.1	127.9	142.5
Demand side management expenses	3.7	3.8	7.6	8.4
Depreciation and amortization	64	57.8	123.1	111
Taxes (other than income taxes)	18.3	17	39.7	35.5
Total operating expenses	343.1	328.6	684.9	708.2
Operating income	80.3	81.9	133.5	156.4
Other income (expense), net	0.1	0.5	(1.9)	0.9
Allowance for funds used during construction — equity	7.8	8.7	13.8	19
Interest charges and financing costs
Interest charges — includes other financing costs of $0.9, $0.8, $1.8 and $1.6, respectively	25.7	25.6	49.9	50
Allowance for funds used during construction — debt	(3.4)	(4.2)	(6)	(8.7)
Total interest charges and financing costs	22.3	21.4	43.9	41.3
Income before income taxes	65.9	69.7	101.5	135
Income tax (benefit) expense	(5.8)	10.9	(12.9)	22.1
Net income	$ 71.7	$ 58.8	$ 114.4	$ 112.9

STATEMENTS OF INCOME (UNAUDIT_2

STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest charges and financing costs
Other financing costs	$ 0.9	$ 0.8	$ 1.8	$ 1.6

STATEMENTS OF COMPREHENSIVE INC

STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Comprehensive income:
Net Income (Loss) Attributable to Parent	$ 71.7	$ 58.8	$ 114.4	$ 112.9
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax	0.1	0	0.1	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0.1	0	0.1
Other comprehensive income	0.1	0.1	0.1	0.1
Comprehensive Income (Loss), Net of Tax, Attributable to Parent, Total	$ 71.8	$ 58.9	$ 114.5	$ 113

STATEMENTS OF COMPREHENSIVE I_2

STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative instruments:
Tax on reclassification of loss to net income	$ 0	$ 0	$ 0	$ 0
Tax on reclassification of loss to net income	$ 0	$ 0	$ 0	$ 0

STATEMENTS OF CASH FLOWS (UNAUD

STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net Income (Loss) Attributable to Parent	$ 114.4	$ 112.9
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	124.3	112.1
Deferred income taxes	11.3	3.3
Allowance for equity funds used during construction	(13.8)	(19)
Provision for Bad Debts	3.1	2.1
Changes in operating assets and liabilities:
Accounts receivable	(5.8)	(3.4)
Increase (Decrease) in Accrued Unbilled Revenues	4.3	11.3
Inventories	(16.2)	(9.9)
Prepayments and other	(3.9)	5.2
Accounts payable	4.2	(24.5)
Net regulatory assets and liabilities	(32.2)	37
Other current liabilities	(7.7)	1.1
Pension and other employee benefit obligations	(14.9)	(16.3)
Other Operating Activities, Cash Flow Statement	1.9	0.7
Net cash provided by operating activities	160.4	190
Investing activities
Utility capital/construction expenditures	(520.4)	(364.2)
Investments in utility money pool arrangement	4	100
Repayments from utility money pool arrangement	4	0
Net cash used in investing activities	(520.4)	(464.2)
Financing activities
Repayments of short-term borrowings, net	0	(42)
Proceeds from Issuance of Long-term Debt	343.3	292.8
Borrowings under utility money pool arrangement	711	283
Repayments under utility money pool arrangement	(711)	(283)
Capital contributions from parent	436	378.8
Dividends paid to parent	(128.9)	(137.7)
Other, net	(0.3)	0
Net cash provided by financing activities	650.1	491.9
Net change in cash, cash equivalents and restricted cash	290.1	217.7
Cash, cash equivalents and restricted cash at beginning of period	16.2	44
Cash, cash equivalents and restricted cash at end of period	306.3	261.7
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(40.4)	(39.9)
Cash received for income taxes, net	4.6	0
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	108.4	68.6
Inventory transfers to property, plant and equipment	13.7	12.6
Operating lease right-of-use assets	0	548.3
Allowance for equity funds used during construction	$ 13.8	$ 19

BALANCE SHEETS (UNAUDITED)

BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 306.3	$ 16.2
Accounts receivable, net	90.1	92.7
Accounts receivable from affiliates	7.3	4.2
Accrued unbilled revenues	119.2	115.1
Inventories	33.5	31
Regulatory assets	21.9	20
Derivative instruments	18.8	15
Prepaid taxes	12.3	0.8
Prepayments and other	14.1	21.4
Total current assets	623.5	316.4
Property, plant and equipment, net	7,105.4	6,631.6
Other assets
Regulatory assets	392.2	364
Derivative instruments	11.1	12.6
Operating lease right-of-use assets	503.8	522.4
Other	3.6	3.9
Total other assets	910.7	902.9
Total assets	8,639.6	7,850.9
Current liabilities
Accounts payable	235.9	168.1
Accounts payable to affiliates	16.5	20.4
Regulatory liabilities	98.9	118.1
Taxes accrued	32.8	40.4
Accrued interest	27.7	26.2
Dividends payable to parent	47.6	46.3
Derivative instruments	3.6	3.7
Operating Lease, Liability, Current	27.5	26.9
Other	26.6	30.7
Total current liabilities	517.1	480.8
Deferred credits and other liabilities
Deferred income taxes	695.9	671.8
Regulatory liabilities	729	732.3
Asset retirement obligations	79.1	77.3
Derivative instruments	11	12.8
Pension and employee benefit obligations	52.1	67
Operating lease liabilities	476.4	495.3
Other	10.5	9.4
Total deferred credits and other liabilities	2,054	2,065.9
Capitalization
Long-term debt	2,763.8	2,419.7
Common stock — 200 shares authorized of $1.00 par value; 100 shares outstanding at June 30, 2020 and Dec. 31, 2019, respectively	0	0
Additional paid in capital	2,786.9	2,350.9
Retained earnings	519.1	535
Accumulated other comprehensive loss	(1.3)	(1.4)
Total common stockholder’s equity	3,304.7	2,884.5
Total liabilities and equity	$ 8,639.6	$ 7,850.9

BALANCE SHEETS (UNAUDITED) (Par

BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Capitalization, Long-term Debt and Equity [Abstract]
Common stock, shares authorized (in shares)	200	200
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares outstanding (in shares)	100	100

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	6 Months Ended
	Jun. 30, 2020
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; and • Level 3 — Significant inputs to pricing have little or no observability as of the reporting date. The types of assets and liabilities included in Level 3 are those valued with models requiring significant management judgment or estimation. Specific valuation methods include: Cash equivalents — The fair values of cash equivalents are generally based on cost plus accrued interest; money market funds are measured using quoted net asset value. Interest rate derivatives — The fair values of interest rate derivatives are based on broker quotes that utilize current market interest rate forecasts. Commodity derivatives — The methods used to measure the fair value of commodity derivative forwards and options utilize forward prices and volatilities, as well as pricing adjustments for specific delivery locations and are generally assigned a Level 2 classification. When contractual settlements relate to inactive delivery locations or extend to periods beyond those readily observable on active exchanges or quoted by brokers, the significance of the use of less observable 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 insignificant to the financial statements of SPS. Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: June 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Fair Value Carrying Fair Value Long-term debt $ 2,763.8 $ 3,249.4 $ 2,419.7 $ 2,706.1 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 June 30, 2020 and Dec. 31, 2019, and given the observability of the inputs, fair values presented for long-term debt were assigned as Level 2.

Selected Balance Sheet Data

Selected Balance Sheet Data	6 Months Ended
	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 96.6 $ 98.0 Less allowance for bad debts (6.5) (5.3) Accounts receivable, net $ 90.1 $ 92.7 (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 26.8 $ 24.7 Fuel 6.7 6.3 Total inventories $ 33.5 $ 31.0 (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 8,690.9 $ 8,453.0 Construction work in progress 802.4 485.4 Total property, plant and equipment 9,493.3 8,938.4 Less accumulated depreciation (2,387.9) (2,306.8) Property, plant and equipment, net $ 7,105.4 $ 6,631.6

Borrowings and Other Financing

Borrowings and Other Financing Instruments	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
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 for SPS were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 100 $ 100 Amount outstanding at period end — — Average amount outstanding 62 8 Maximum amount outstanding 100 100 Weighted average interest rate, computed on a daily basis 0.83 % 2.42 % Weighted average interest rate at period end N/A N/A Commercial Paper — Commercial paper outstanding for SPS was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 500 $ 500 Amount outstanding at period end — — Average amount outstanding 53 72 Maximum amount outstanding 138 316 Weighted average interest rate, computed on a daily basis 1.09 % 2.68 % Weighted average interest rate at period end N/A N/A Letters of Credit — SPS uses letters of credit, generally with terms of one year, to provide financial guarantees for certain operating obligations. At both June 30, 2020 and Dec. 31, 2019, 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. Revolving 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. SPS has the right to request an extension of the revolving credit facility termination date for two additional one-year periods. All extension requests are subject to majority bank group approval. As of June 30, 2020, SPS had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 500 $ 2 $ 498 (a) This credit facility expires in June 2024. (b) Includes outstanding letters of credit. 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 credit facility outstanding as of June 30, 2020 and Dec. 31, 2019. Long-Term Borrowings During the six months ended June 30, 2020, SPS issued $350 million of 3.15% first mortgage bonds due May 1, 2050.

Revenues

Revenues	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue	Revenue is classified by the type of goods/services rendered and market/customer type. SPS’ operating revenues consists of the following: Three Months Ended (Millions of Dollars) June 30, 2020 June 30, 2019 Major revenue types Revenue from contracts with customers: Residential $ 84.8 $ 70.4 C&I 163.7 191.4 Other 8.7 9.9 Total retail 257.2 271.7 Wholesale 81.6 72.0 Transmission 76.0 60.0 Other 0.6 0.4 Total revenue from contracts with customers 415.4 404.1 Alternative revenue and other 8.0 6.4 Total revenues $ 423.4 $ 410.5 Six Months Ended (Millions of Dollars) June 30, 2020 June 30, 2019 Major revenue types Revenue from contracts with customers: Residential $ 157.7 $ 158.5 C&I 332.8 397.2 Other 16.6 19.5 Total retail 507.1 575.2 Wholesale 154.8 156.8 Transmission 138.6 117.4 Other 1.2 1.4 Total revenue from contracts with customers 801.7 850.8 Alternative revenue and other 16.7 13.8 Total revenues $ 818.4 $ 864.6

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes Note 7 to the financial statements included in SPS’ Annual Report on Form 10-K for the year ended Dec. 31, 2019 represents, in all material respects, the current status of other income tax matters except to the extent noted below, and are incorporated herein by reference. The following table reconciles the difference between the statutory rate and the ETR: Six Months Ended June 30, 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 2.3 2.1 Decreases in tax from: Wind PTCs (26.7) (0.2) Plant regulatory differences (a) (6.4) (4.8) Prior period adjustments (2.0) (0.7) Other tax credits, net of NOL & tax credit allowances (0.7) (0.6) Other (net) (0.2) (0.4) Effective income tax rate (12.7) % 16.4 % (a) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions. Federal Audits — SPS is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021 In 2017, the IRS concluded the audit of tax years 2012 and 2013 and proposed an adjustment that would impact Xcel Energy’s NOL and ETR. Xcel Energy filed a protest with the IRS. In April 2020 , Xcel Energy and Appeals reached an agreement and no material adjustments were required. In 2018, the IRS began an audit of tax years 2014 - 2016. As of June 30, 2020, no adjustments have been proposed. State Audits — SPS is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of June 30, 2020, SPS’ earliest open tax year subject to examination by state taxing authorities under applicable statutes of limitations is 2009. There are currently no state income tax audits in progress. Unrecognized Benefits — Unrecognized tax benefit balance includes permanent tax positions, which if recognized would affect the annual ETR. In addition, the unrecognized tax benefit balance includes temporary tax positions for which ultimate deductibility is highly certain, but for which there is uncertainty about the timing of such deductibility. A change in the period of deductibility would not affect the ETR but would accelerate the payment to the taxing authority to an earlier period. Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 3.6 $ 3.7 Unrecognized tax benefit — Temporary tax positions 1.5 1.5 Total unrecognized tax benefit $ 5.1 $ 5.2 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) June 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (4.5) $ (4.4) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credits carryforwards were $1.8 million and $1.4 million at June 30, 2020 and Dec. 31, 2019, respectively. As the IRS audit progresses and state audits resume, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $2.9 million in the next 12 months. Payables for interest related to unrecognized tax benefits were not material and no amounts were accrued for penalties related to unrecognized tax benefits as of June 30, 2020 and Dec. 31, 2019, respectively.

Benefit Plans and Other Postret

Benefit Plans and Other Postretirement Benefits	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost (Credit) Three Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 2.4 $ 2.2 $ 0.2 $ 0.2 Interest cost (a) 4.5 5.0 0.4 0.4 Expected return on plan assets (a) (7.4) (7.2) (0.5) (0.5) Amortization of prior service credit (a) — — (0.1) (0.1) Amortization of net loss (gain) (a) 3.3 2.9 (0.1) (0.1) Net periodic benefit cost (credit) 2.8 2.9 (0.1) (0.1) Credits not recognized due to effects 0.5 0.4 — — Net benefit cost (credit) recognized for financial reporting $ 3.3 $ 3.3 $ (0.1) $ (0.1) Six Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 4.8 $ 4.4 $ 0.5 $ 0.4 Interest cost (a) 9.0 10.1 0.7 0.9 Expected return on plan assets (a) (14.7) (14.3) (0.9) (1.0) Amortization of prior service credit (a) (0.1) (0.1) (0.2) (0.3) Amortization of net loss (gain) (a) 6.6 5.7 (0.2) (0.2) Net periodic benefit cost (credit) 5.6 5.8 (0.1) (0.2) Credits not recognized due to effects 1.0 0.8 — — Net benefit cost (credit) recognized for financial reporting $ 6.6 $ 6.6 $ (0.1) $ (0.2) (a) The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the income statement or capitalized on the balance sheet as a regulatory asset.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	The following include commitments, contingencies and unresolved contingencies that are material to SPS’ financial position. 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 of such matters, 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. Unless otherwise required by GAAP, legal fees are expensed as incurred. Rate Matters SPP OATT Upgrade Costs — Under the SPP OATT, costs of transmission upgrades may be recovered from other SPP customers whose transmission service depends on capacity enabled by the upgrade. 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 these previously unbilled charges was remanded to the FERC. In February 2019, the FERC reversed its 2016 decision and ordered SPP to refund the charges retroactively collected from its transmission customers, including SPS, related to periods before September 2015. In April 2019, several parties, including SPP, filed requests for a rehearing. In February 2020, FERC issued an order rejecting all rehearing requests and providing certain clarifications. In March 2020, SPP and Oklahoma Gas & Electric separately filed petitions for review of FERC’s orders at the D.C. Circuit. SPS has intervened in both appeals in support of FERC. The timing of an appeals decision is uncertain. Any refunds received by SPS are expected to be given back to SPS customers through future rates. In October 2017, SPS filed a separate related complaint against SPP asserting that SPP has assessed upgrade charges to SPS in violation of the SPP OATT. In March 2018, FERC issued an order denying the SPS complaint in its entirety, and finding SPP’s calculations to be consistent with the SPP Tariff. 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 amounts through future SPS customer rates . In June 2020, the D.C. Circuit issued a decision in an unrelated proceeding (Allegheny Defense Project v. FERC), which held that FERC’s longstanding use of tolling orders to extend FERC’s deadline to act on the merits of requests for rehearing is improper. The effect on this decision on tolling orders previously issued by FERC is unclear. SPP Filing to Assign GridLiance Facilities to SPS Rate Zone — In August 2018, SPP filed a request with the FERC to amend its OATT to include the costs of the GridLiance High Plains, LLC facilities in the SPS rate zone. In a previous filing, the FERC determined that some of these facilities did not qualify as transmission facilities under the SPP OATT. SPP’s proposed tariff changes resulted in an increase in the annual transmission revenue requirement of $9.5 million per year, with $6 million allocated to SPS’ retail customers. The remaining $3.5 million would be paid by other wholesale loads in the SPS rate zone. In September 2018, SPS protested the proposed SPP tariff charges, and asked the FERC to reject the SPP filing. On Oct. 31, 2018, the FERC issued an order accepting the proposed charges, subject to refund, as of Nov. 1, 2018, and set the case for settlement hearing procedures. Hearings are scheduled to begin in August 2020, and the ALJ’s initial decision is expected in February 2021. In addition, the chief ALJ has appointed a new settlement judge who has ordered additional settlement discussions prior to the scheduled hearing date. SPS has incurred approximately $10.2 million in associated charges as of June 30, 2020. SPS Filing to Modify Wholesale Transmission Rates — In 2018, SPS filed revisions to its wholesale transmission formula rate. The proposal includes an update to the depreciation rates for transmission plant. The new formula rate would also provide a credit to customers of “excess” accumulated deferred income tax resulting from the TCJA and recover certain wholesale regulatory commission expenses. The proposed changes would increase wholesale transmission revenues by approximately $9.4 million, with approximately $4.4 million of the total being recovered in SPP regional transmission rates. SPS proposed that the formula rate changes be effective Feb. 1, 2019. In January 2019, the FERC issued an order accepting the proposed rate changes as of Feb. 1, 2019, subject to refund and settlement procedures. On Dec. 23, 2019, SPS filed a Stipulation and Agreement of Settlement, which was approved by the FERC in April 2020. Environmental Manufactured Gas Plant, Landfill and Disposal Sites — SPS is currently remediating a former disposal site. SPS has recognized its best estimate of costs/liabilities that will result from final resolution of these issues, however, the outcome and timing is unknown. In addition, there may be insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of costs incurred. VIEs 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. These specific PPAs create a variable interest in the IPP. SPS had approximately 1,197 MW of capacity under long-term PPAs at June 30, 2020 and Dec. 31, 2019 with entities that have been determined to be VIEs. 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. Agreements have expiration dates through 2041.

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	6 Months Ended
	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 96.6 $ 98.0 Less allowance for bad debts (6.5) (5.3) Accounts receivable, net $ 90.1 $ 92.7
Inventories	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 26.8 $ 24.7 Fuel 6.7 6.3 Total inventories $ 33.5 $ 31.0
Property, Plant and Equipment, Net	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 8,690.9 $ 8,453.0 Construction work in progress 802.4 485.4 Total property, plant and equipment 9,493.3 8,938.4 Less accumulated depreciation (2,387.9) (2,306.8) Property, plant and equipment, net $ 7,105.4 $ 6,631.6

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	As of June 30, 2020, SPS had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 500 $ 2 $ 498 (a) This credit facility expires in June 2024. (b) Includes outstanding letters of credit.
Money Pool
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Money pool borrowings for SPS were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 100 $ 100 Amount outstanding at period end — — Average amount outstanding 62 8 Maximum amount outstanding 100 100 Weighted average interest rate, computed on a daily basis 0.83 % 2.42 % Weighted average interest rate at period end N/A N/A
Commercial Paper
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Commercial paper outstanding for SPS was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 500 $ 500 Amount outstanding at period end — — Average amount outstanding 53 72 Maximum amount outstanding 138 316 Weighted average interest rate, computed on a daily basis 1.09 % 2.68 % Weighted average interest rate at period end N/A N/A

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	SPS’ operating revenues consists of the following: Three Months Ended (Millions of Dollars) June 30, 2020 June 30, 2019 Major revenue types Revenue from contracts with customers: Residential $ 84.8 $ 70.4 C&I 163.7 191.4 Other 8.7 9.9 Total retail 257.2 271.7 Wholesale 81.6 72.0 Transmission 76.0 60.0 Other 0.6 0.4 Total revenue from contracts with customers 415.4 404.1 Alternative revenue and other 8.0 6.4 Total revenues $ 423.4 $ 410.5 Six Months Ended (Millions of Dollars) June 30, 2020 June 30, 2019 Major revenue types Revenue from contracts with customers: Residential $ 157.7 $ 158.5 C&I 332.8 397.2 Other 16.6 19.5 Total retail 507.1 575.2 Wholesale 154.8 156.8 Transmission 138.6 117.4 Other 1.2 1.4 Total revenue from contracts with customers 801.7 850.8 Alternative revenue and other 16.7 13.8 Total revenues $ 818.4 $ 864.6

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table reconciles the difference between the statutory rate and the ETR: Six Months Ended June 30, 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 2.3 2.1 Decreases in tax from: Wind PTCs (26.7) (0.2) Plant regulatory differences (a) (6.4) (4.8) Prior period adjustments (2.0) (0.7) Other tax credits, net of NOL & tax credit allowances (0.7) (0.6) Other (net) (0.2) (0.4) Effective income tax rate (12.7) % 16.4 % (a)
Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]	Federal Audits — SPS is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 3.6 $ 3.7 Unrecognized tax benefit — Temporary tax positions 1.5 1.5 Total unrecognized tax benefit $ 5.1 $ 5.2
Tax Benefits Associated with NOL and Tax Credit Carryforwards	Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) June 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (4.5) $ (4.4)

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Gross Notional Amounts of Commodity FTRs	(Amounts in Millions) (a) June 30, 2020 Dec. 31, 2019 MWh of electricity 11.9 6.4 (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	Recurring Fair Value Measurements — SPS’ derivative assets and liabilities measured at fair value on a recurring basis: June 30, 2020 Dec. 31, 2019 Fair Value Fair Value (Millions of Dollars) Level 1 Level 2 Level 3 Fair Value Netting (a) Total Level 1 Level 2 Level 3 Fair Value Netting (a) Total Current derivative assets Other derivative instruments: Electric commodity $ — $ — $ 15.9 $ 15.9 $ (0.2) $ 15.7 $ — $ — $ 11.8 $ 11.8 $ — $ 11.8 Total current derivative assets $ — $ — $ 15.9 $ 15.9 $ (0.2) 15.7 $ — $ — $ 11.8 $ 11.8 $ — 11.8 PPAs (b) 3.1 3.2 Current derivative instruments $ 18.8 $ 15.0 Noncurrent derivative assets PPAs (b) $ 11.1 $ 12.6 Noncurrent derivative instruments $ 11.1 $ 12.6 June 30, 2020 Dec. 31, 2019 Fair Value Fair Value (Millions of Dollars) Level 1 Level 2 Level 3 Fair Value Netting (a) Total Level 1 Level 2 Level 3 Fair Value Netting (a) Total Current derivative liabilities Other derivative instruments: Electric commodity $ — $ — $ 0.2 $ 0.2 $ (0.2) $ — $ — $ — $ 0.1 $ 0.1 $ — $ 0.1 Total current derivative liabilities $ — $ — $ 0.2 $ 0.2 $ (0.2) — $ — $ — $ 0.1 $ 0.1 $ — 0.1 PPAs (b) 3.6 . 3.6 Current derivative instruments $ 3.6 $ 3.7 Noncurrent derivative liabilities PPAs (b) $ 11.0 $ 12.8 Noncurrent derivative instruments $ 11.0 $ 12.8 (a) SPS nets derivative instruments and related collateral in its balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at June 30, 2020 and Dec. 31, 2019. At both June 30, 2020 and Dec. 31, 2019, derivative assets and liabilities include no obligations to return cash collateral or rights to reclaim cash collateral. 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 three and six months ended June 30, 2020 and 2019: Three Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at April 1 $ 16.3 $ 3.1 Purchases 9.0 17.1 Settlements (11.9) (13.1) Net transactions recorded during the period: Net gains recognized as regulatory assets and liabilities 2.3 15.1 Balance at June 30 $ 15.7 $ 22.2 Six Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ 11.7 $ 14.7 Purchases 20.8 21.0 Settlements (16.8) (19.7) Net transactions recorded during the period: Net gains recognized as regulatory assets and liabilities — 6.2 Balance at June 30 $ 15.7 $ 22.2
Carrying Amount and Fair Value of Long-term Debt	Other financial instruments for which the carrying amount did not equal fair value: June 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Fair Value Carrying Fair Value Long-term debt $ 2,763.8 $ 3,249.4 $ 2,419.7 $ 2,706.1

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost (Credit)	Components of Net Periodic Benefit Cost (Credit) Three Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 2.4 $ 2.2 $ 0.2 $ 0.2 Interest cost (a) 4.5 5.0 0.4 0.4 Expected return on plan assets (a) (7.4) (7.2) (0.5) (0.5) Amortization of prior service credit (a) — — (0.1) (0.1) Amortization of net loss (gain) (a) 3.3 2.9 (0.1) (0.1) Net periodic benefit cost (credit) 2.8 2.9 (0.1) (0.1) Credits not recognized due to effects 0.5 0.4 — — Net benefit cost (credit) recognized for financial reporting $ 3.3 $ 3.3 $ (0.1) $ (0.1) Six Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 4.8 $ 4.4 $ 0.5 $ 0.4 Interest cost (a) 9.0 10.1 0.7 0.9 Expected return on plan assets (a) (14.7) (14.3) (0.9) (1.0) Amortization of prior service credit (a) (0.1) (0.1) (0.2) (0.3) Amortization of net loss (gain) (a) 6.6 5.7 (0.2) (0.2) Net periodic benefit cost (credit) 5.6 5.8 (0.1) (0.2) Credits not recognized due to effects 1.0 0.8 — — Net benefit cost (credit) recognized for financial reporting $ 6.6 $ 6.6 $ (0.1) $ (0.2) (a) The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the income statement or capitalized on the balance sheet as a regulatory asset.	[1]
[1]	The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the income statement or capitalized on the balance sheet as a regulatory asset.

Accounting Pronouncements (Deta

Accounting Pronouncements (Details) - USD ($) $ in Millions	Jan. 01, 2020	Jun. 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)		$ 0.1
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)	$ 0.1	$ 0.1

Selected Balance Sheet Data Acc

Selected Balance Sheet Data Accounts Receivable, Net (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Accounts receivable, net
Accounts receivable	$ 96.6	$ 98
Less allowance for bad debts	(6.5)	(5.3)
Accounts receivable, net	$ 90.1	$ 92.7

Selected Balance Sheet Data Sel

Selected Balance Sheet Data Selected Balance Sheet Data Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Inventories	$ 33.5	$ 31
Inventory, Net	33.5	31
Materials and supplies
Inventories	26.8	24.7
Fuel
Inventories	$ 6.7	$ 6.3

Selected Balance Sheet Data Bal

Selected Balance Sheet Data Balance Sheet Related Disclosures, Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 9,493.3	$ 8,938.4
Accumulated depreciation	(2,387.9)	(2,306.8)
Property, plant and equipment, net	7,105.4	6,631.6
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,690.9	8,453
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 802.4	$ 485.4

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments - Money Pool (Details) - Money Pool - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Borrowing limit	$ 100,000,000	$ 100,000,000
Amount outstanding at period end	0	0
Average amount outstanding	62,000,000	8,000,000
Maximum amount outstanding	$ 100,000,000	$ 100,000,000
Weighted average interest rate, computed on a daily basis	0.83%	2.42%

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments - Commercial Paper (Details) - Commercial Paper - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Borrowing limit	$ 500,000,000	$ 500,000,000
Amount outstanding at period end	0	0
Average amount outstanding	53,000,000	72,000,000
Maximum amount outstanding	$ 138,000,000	$ 316,000,000
Weighted average interest rate, computed on a daily basis	1.09%	2.68%

Borrowings and Other Financin_5

Borrowings and Other Financing Instruments - Letters of Credit (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 2,000,000	$ 2,000,000
Debt Instrument, Term	1 year
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Direct advances on the credit facility outstanding	$ 0	$ 0

Borrowings and Other Financin_6

Borrowings and Other Financing Instruments - Credit Facility (Details) - Credit Facility - USD ($)		Jun. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 500,000,000
Outstanding	[2]	2,000,000
Available		498,000,000
Direct advances on the credit facility outstanding		$ 0	$ 0
[1]	This credit facility expires in June 2024
[2]	Includes outstanding letters of credit.

Borrowings and Other Financin_7

Borrowings and Other Financing Instruments - Long-Term Borrowings (Details) - Series due 2050 [Domain] - Bonds [Member] $ in Millions	May 18, 2020USD ($)
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350
Debt Instrument, Interest Rate, Stated Percentage	3.15%

Revenues (Details)

Revenues (Details) - Regulated Electric - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 415.4	$ 404.1	$ 801.7	$ 850.8
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	423.4	410.5	818.4	864.6
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	257.2	271.7	507.1	575.2
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	84.8	70.4	157.7	158.5
Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	163.7	191.4	332.8	397.2
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8.7	9.9	16.6	19.5
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81.6	72	154.8	156.8
Transmission
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	60	138.6	117.4
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0.6	0.4	1.2	1.4
Alternative and Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 8	$ 6.4	$ 16.7	$ 13.8

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Federal statutory rate, percent		21.00%	21.00%
State tax (net of federal tax effect), percent		2.30%	2.10%
Wind PTCs, percent		(26.70%)	(0.20%)
Plant regulatory differences, percent	[1]	(6.40%)	(4.80%)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent		(2.00%)	(0.70%)
Other tax credits, percent		(0.70%)	(0.60%)
Other (net), percent		(0.20%)	(0.40%)
Effective income tax rate, percent		(12.70%)	16.40%
Income Tax Credits and Adjustments		$ 0
[1]	Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.

Income Taxes Unrecognized Benef

Income Taxes Unrecognized Benefits (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefit - Permanent tax positions	$ 3,600,000	$ 3,700,000
Unrecognized tax benefit - Temporary tax positions	1,500,000	1,500,000
Total unrecognized tax benefit	5,100,000	5,200,000
NOL and tax credit carryforwards	4,500,000	4,400,000
Related NOLs and tax credit carryforwards	(1,800,000)	(1,400,000)
Reasonably possible decrease in unrecognized tax benefits	2,900,000
Penalties related to unrecognized tax benefits	0	0
Penalties related to unrecognized tax benefits	$ 0	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Interest Rate Derivatives (Details) $ in Millions	Jun. 30, 2020USD ($)
Interest Rate Swap [Member]
Derivative [Line Items]
Interest rate derivatives net losses reclassified during next 12 months	$ 0.1

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Commodity Derivatives (Details) - MWh MWh in Millions		Jun. 30, 2020	Dec. 31, 2019
Electric Commodity [Member]
Derivative [Line Items]
Mwh of electricity	[1]	11.9	6.4
[1]	Amounts are not reflective of net positions in the underlying commodities.

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Consideration of Credit Risk Concentrations (Details) - Credit Concentration Risk $ in Millions	Jun. 30, 2020USD ($)Counterparty
Derivative [Line Items]
Significant counterparties	9
Municipal or cooperative electric entities or other utilities
Derivative [Line Items]
Significant counterparties	9
External credit rating, investment grade
Derivative [Line Items]
Significant counterparties	2
Credit exposure | $	$ 14.8
Credit exposure, percentage	36.00%
Internal investment grade
Derivative [Line Items]
Significant counterparties	6
Credit exposure | $	$ 26
Credit exposure, percentage	64.00%
External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Significant counterparties	1
Credit exposure | $	$ 0.1
Credit exposure, percentage	0.20%

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities - Impact of Derivative Activities on Income and Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Derivative instruments designated as fair value hedges	$ 0	$ 0	$ 0	$ 0
Other Derivative Instruments | Electric Commodity
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Changes in fair value of FTRs pre-tax gains	2.6	9.9	2.5	4.6
FTR settlement gains	$ 2.3	$ 0.2	$ 5.1	$ 0.2

Fair Value of Financial Asset_7

Fair Value of Financial Assets and Liabilities - Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivatives, Fair Value
Return Cash Collateral		$ 0		$ 0		$ 0
Reclaim Cash Collateral		0		0		0
Commodity Contract [Member]
Changes in Level 3 Commodity Derivatives
Balance at beginning of period		16.3	$ 3.1	11.7	$ 14.7
Purchases		9	17.1	20.8	21
Settlements		(11.9)	(13.1)	(16.8)	(19.7)
Net gains recognized as regulatory assets and liabilities		2.3	15.1	0	6.2
Balance at end of period		15.7	22.2	15.7	22.2
Transfers Level 3, Net		0	$ 0	0	$ 0
Other Current Assets
Derivatives, Fair Value
Derivative asset, net		18.8		18.8		15
Other Noncurrent Assets
Derivatives, Fair Value
Derivative asset, net		11.1		11.1		12.6
Other Current Liabilities
Derivatives, Fair Value
Derivative liability, net		3.6		3.6		3.7
Other Noncurrent Liabilities
Derivatives, Fair Value
Derivative liability, net		11		11		12.8
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value
Derivative asset, gross		15.9		15.9		11.8
Asset, netting	[1]	(0.2)		(0.2)		0
Derivative asset, net		15.7		15.7		11.8
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value
Derivative asset, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value
Derivative asset, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value
Derivative asset, gross		15.9		15.9		11.8
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity
Derivatives, Fair Value
Derivative asset, gross		15.9		15.9		11.8
Asset, netting	[1]	(0.2)		(0.2)		0
Derivative asset, net		15.7		15.7		11.8
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 1 | Electric Commodity
Derivatives, Fair Value
Derivative asset, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 2 | Electric Commodity
Derivatives, Fair Value
Derivative asset, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 3 | Electric Commodity
Derivatives, Fair Value
Derivative asset, gross		15.9		15.9		11.8
Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value
Derivative liability, gross		0.2		0.2		0.1
Liabilities, netting	[1]	(0.2)		(0.2)		0
Derivative liability, net		0		0		0.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 1
Derivatives, Fair Value
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 2
Derivatives, Fair Value
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 3
Derivatives, Fair Value
Derivative liability, gross		0.2		0.2		0.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Electric Commodity
Derivatives, Fair Value
Derivative liability, gross		0.2		0.2		0.1
Liabilities, netting	[1]	(0.2)		(0.2)		0
Derivative liability, net		0		0		0.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 1 | Electric Commodity
Derivatives, Fair Value
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 2 | Electric Commodity
Derivatives, Fair Value
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 3 | Electric Commodity
Derivatives, Fair Value
Derivative liability, gross		0.2		0.2		0.1
Fair Value, Measurements, Nonrecurring | Other Current Assets | PPAs
Derivatives, Fair Value
Derivative asset, net	[2]	3.1		3.1		3.2
Fair Value, Measurements, Nonrecurring | Other Noncurrent Assets | PPAs
Derivatives, Fair Value
Derivative asset, net	[2]	11.1		11.1		12.6
Fair Value, Measurements, Nonrecurring | Other Current Liabilities | PPAs
Derivatives, Fair Value
Derivative liability, net	[2]	3.6		3.6		3.6
Fair Value, Measurements, Nonrecurring | Other Noncurrent Liabilities | PPAs
Derivatives, Fair Value
Derivative liability, net	[2]	$ 11		$ 11		$ 12.8
[1]	SPS nets derivative instruments and related collateral in its balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at June 30, 2020 and Dec. 31, 2019. At both June 30, 2020 and Dec. 31, 2019, derivative assets and liabilities include no obligations to return cash collateral or rights to reclaim cash collateral. 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 Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	$ 2,763.8	$ 2,419.7
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 3,249.4	$ 2,706.1

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
		Jan. 31, 2020USD ($)Plan	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 2.4	$ 2.2	$ 4.8	$ 4.4
Interest cost (a)	[1]		4.5	5	9	10.1
Expected return on plan assets (a)	[1]		(7.4)	(7.2)	(14.7)	(14.3)
Amortization of prior service credit (a)	[1]		0	0	(0.1)	(0.1)
Amortization of net loss (gain) (a)	[1]		3.3	2.9	6.6	5.7
Net periodic benefit cost (credit)			2.8	2.9	5.6	5.8
Credits not recognized due to effects of regulation			0.5	0.4	1	0.8
Net benefit cost (credit) recognized for financial reporting			3.3	3.3	6.6	6.6
Contributions to pension plans		$ 14.4
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Contributions to pension plans		$ 150
Number of pension plans to which contributions were made | Plan		4
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.2	0.2	0.5	0.4
Interest cost (a)	[1]		0.4	0.4	0.7	0.9
Expected return on plan assets (a)	[1]		(0.5)	(0.5)	(0.9)	(1)
Amortization of prior service credit (a)	[1]		(0.1)	(0.1)	(0.2)	(0.3)
Amortization of net loss (gain) (a)	[1]		(0.1)	(0.1)	(0.2)	(0.2)
Net periodic benefit cost (credit)			(0.1)	(0.1)	(0.1)	(0.2)
Credits not recognized due to effects of regulation			0	0	0	0
Net benefit cost (credit) recognized for financial reporting			$ (0.1)	$ (0.1)	$ (0.1)	$ (0.2)
[1]	The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the income statement or capitalized on the balance sheet as a regulatory asset.

Commitments and Contingencies -

Commitments and Contingencies - SPP OATT Upgrade Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Southwest Power Pool (SPP) | SPP Open Access Transmission Tariff Upgrade Costs
Public Utilities, General Disclosures [Line Items]
Charges For Transmission Service Upgrades	$ 13

Commitments and Contingencies_2

Commitments and Contingencies - SPP Filing to Assign GridLiance Facilities to SPS Rate Zone (Details) - Southwest Power Pool (SPP) - SPP Open Access Transmission Tariff Upgrade Costs - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Aug. 31, 2018	Jun. 30, 2020
Public Utilities, General Disclosures [Line Items]
Annual Transmission Revenue Requirement Increase	$ 9.5
Annual Transmission Revenue Requirement Increase (SPS)	6	$ 10.2
Annual Transmission Revenue Requirement (Other Utilities)	$ 3.5

Commitments and Contingencies_3

Commitments and Contingencies - SPS Filing to Modify Wholesale Transmission Rates (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Public Utilities, General Disclosure [Abstract]
Amount proposed changes would increase wholesale transmission revenues	$ 9.4
Amount of proposed changes would be recoverable	$ 4.4

Commitments and Contingencies_4

Commitments and Contingencies - Variable Interest Entities (Details) - MW	Jun. 30, 2020	Dec. 31, 2019
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Purchased Power Agreements [Abstract]
Generating capacity (in MW)	1,197	1,197

Other Comprehensive Income (Det

Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income Tax Expense (Benefit)	$ (5.8)	$ 10.9	$ (12.9)	$ 22.1
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period			2,884.5
Accumulated other comprehensive loss at end of period	$ 3,304.7		$ 3,304.7