Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Estimated Minimum Purchases Under Fuel Contracts

The estimated minimum purchases for SPS under these contracts as of Dec. 31, 2017, are as follows:

(Millions of Dollars)	Coal		Natural gas supply		Natural gas storage and transportation
2018	$	172	$	11	$	29
2019	106		—		32
2020	64		—		32
2021	20		—		27
2022	21		—		21
Thereafter	—		—		50
Total	$	383	$	11	$	191

Estimated Future Payments for Capacity and Energy Pursuant to Purchased Power Agreements

At Dec. 31, 2017, the estimated future payments for capacity that SPS is obligated to purchase pursuant to these executory contracts, subject to availability, are as follows:

(Millions of Dollars)	Capacity
2018	$	58
2019	20
2020	12
2021	12
2022	13
Thereafter	18
Total	$	133

Future Commitments Under Operating Leases

Future commitments under operating leases are:

(Millions of Dollars)	Operating Leases		PPA (a) (b) Operating Leases		Total Operating Leases
2018	$	5	$	52	$	57
2019	5		51		56
2020	5		51		56
2021	5		51		56
2022	5		51		56
Thereafter	61		543		604

^(a)  Amounts do not include PPAs accounted for as executory contracts.

^(b)  PPA operating leases contractually expire through 2033.

Asset Retirement Obligations

A reconciliation of SPS’ AROs for the years ended Dec. 31, 2017 and 2016 is as follows:

(Thousands of Dollars)	Beginning Balance Jan. 1, 2017		Accretion		Cash Flow Revisions (a)			Ending Balance     Dec. 31, 2017 (b)
Electric plant
Steam production asbestos	$	19,070	$	1,155	$	(1,676	)	$	18,549
Electric distribution	6,799		249		—			7,048
Steam production ash containment	1,593		85		—			1,678
Other	1,201		48		—			1,249
Total liability	$	28,663	$	1,537	$	(1,676	)	$	28,524

^(a)  In 2017, an asbestos ARO was revised for changes in timing of estimated cash flows.

^(b)  There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2017.

(Thousands of Dollars)	Beginning Balance Jan. 1, 2016		Accretion		Cash Flow Revisions			Ending Balance     Dec. 31, 2016 (a)
Electric plant
Steam production asbestos	$	17,981	$	1,089	$	—		$	19,070
Steam production ash containment	1,513		80		—			1,593
Electric distribution	6,559		240		—			6,799
Other	1,180		42		(21		)	1,201
Total liability	$	27,233	$	1,451	$	(21	)	$	28,663

^(a)  There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2016.