Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2015

Commitments and Contingencies Disclosure [Abstract]

Estimated Minimum Purchases Under Fuel Contracts

The estimated minimum purchases for PSCo under these contracts as of Dec. 31, 2015, are as follows:

(Millions of Dollars)	Coal		Natural gas supply		Natural gas storage and transportation
2016	$	302.3	$	231.1	$	137.5
2017	230.3		129.5		137.2
2018	118.5		181.0		85.5
2019	42.0		187.6		51.0
2020	43.6		203.4		50.4
Thereafter	332.3		409.6		773.2
Total	$	1,069.0	$	1,342.2	$	1,234.8

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

At Dec. 31, 2015, the estimated future payments for capacity and energy that PSCo is obligated to purchase pursuant to these executory contracts, subject to availability, are as follows:

(Millions of Dollars)	Capacity		Energy (a)
2016	$	44.5	$	25.3
2017	24.3		4.4
2018	19.2		—
2019	10.3		—
2020	1.5		—
Thereafter	9.5		—
Total	$	109.3	$	29.7

^(a)  Excludes contingent energy payments for renewable energy PPAs.

Summary of Property Held Under Capital Leases

Total amortization expenses under capital lease assets were approximately $8.2 million, $7.2 million, and $6.3 million for 2015, 2014 and 2013, respectively. Following is a summary of property held under capital leases:

(Millions of Dollars)	Dec. 31, 2015			Dec. 31, 2014
Gas storage facilities	$	200.5		$	200.5
Gas pipeline	20.7			20.7
Property held under capital leases	221.2			221.2
Accumulated depreciation	(57.2		)	(49.0		)
Total property held under capital leases, net	$	164.0		$	172.2

Future Commitments Under Operating and Capital Leases

Future commitments under operating and capital leases are:

(Millions of Dollars)	Operating Leases		PPA (a) (b) Operating Leases		Total Operating Leases		Capital Leases
2016	$	12.0	$	102.2	$	114.2	$	29.3
2017	7.8		95.8		103.6		25.7
2018	7.4		96.0		103.4		25.3
2019	7.4		96.9		104.3		25.1
2020	7.4		97.7		105.1		24.9
Thereafter	39.5		579.7		619.2		486.5
Total minimum obligation							616.8
Interest component of obligation							(452.8		)
Present value of minimum obligation							$	164.0

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

^(b)  PPA operating leases contractually expire through 2032.

Asset Retirement Obligations

A reconciliation of PSCo’s AROs for the years ended Dec. 31, 2015 and 2014 is as follows:

(Thousands of Dollars)	Beginning Balance Jan. 1, 2015		Accretion		Cash Flow     Revisions (a)			Ending Balance      Dec. 31, 2015 (b)
Electric plant
Steam and other production asbestos	$	36,856	$	1,820	$	—		$	38,676
Steam and other production ash containment	61,885		2,769		6,113			70,767
Wind production	2,095		18		(121		)	1,992
Electric distribution	1,182		47		(99		)	1,130
Other	1,150		46		(142		)	1,054
Natural gas plant
Gas transmission and distribution	117,474		4,694		—			122,168
Other	3,886		153		(114		)	3,925
Common and other property
Common miscellaneous	768		28		—			796
Total liability	$	225,296	$	9,575	$	5,637		$	240,508

^(a)  In 2015, AROs were revised for changes in estimated cash flows and the timing of those cash flows. Changes in the ash containment ARO were mainly related to the final coal ash rule mentioned above.

^(b)  There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2015.

(Thousands of Dollars)	Beginning Balance Jan. 1, 2014		Liabilities Recognized		Accretion		Cash Flow    Revisions (a)			Ending Balance  Dec. 31, 2014 (b)
Electric plant
Steam and other production asbestos	$	23,914	$	747	$	1,597	$	10,598		$	36,856
Steam and other production ash containment	29,234		—		1,897		30,754			61,885
Wind production	2,953		—		22		(880		)	2,095
Electric distribution	1,176		—		43		(37		)	1,182
Other	1,017		—		41		92			1,150
Natural gas plant
Gas transmission and distribution	788		18,252		50		98,384			117,474
Other	575		2,865		24		422			3,886
Common and other property
Common miscellaneous	741		—		27		—			768
Total liability	$	60,398	$	21,864	$	3,701	$	139,333		$	225,296