UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Tables)

12 Months Ended

Dec. 31, 2021

Regulated Operations [Abstract]

Public utility PPE

The following table shows Plant in Service on the Consolidated Balance Sheets by major class:

	Annual Depreciation Rate (3)	Average Remaining Life in Years (3)	December 31,
($ in millions)			2021		2020
Plant in Service
Generation Plant	3.11%	18	$	3,753	$	3,279
Distribution Plant	1.93%	33	2,024		1,906
Transmission Plant	1.69%	35	1,210		1,090
General Plant	6.01%	7	540		503
Intangible Plant, Software Costs, and Other (1)	Various	Various	268		291
Plant Held for Future Use	—	—	3		4
Total Plant in Service (2)			$	7,798	$	7,073

(1)Primarily represents computer software, which is amortized over three to five years for smaller application software and 10 years for large enterprise software and has an average remaining life of three years.

(2)Includes plant acquisition adjustments of $(206) million and $(202) million as of December 31, 2021 and 2020, respectively.

(3)Based on the 2018 depreciation study available for the major classes of Plant in Service, effective January 1, 2021, as approved as part of the 2020 Rate Order. Transmission Plant depreciation rates are based on the 2018 depreciation study, effective August 1, 2019, as approved as part of the 2019 FERC Rate Case.

Schedule of jointly owned utility plants

As of December 31, 2021, TEP was a participant in the following jointly-owned generation facilities and transmission systems:

($ in millions)	Ownership Percentage	Plant in Service		Construction Work in Progress		Accumulated Depreciation		Net Book Value
San Juan Unit 1	50.0%	$	285	$	1	$	(269)	$	17
Four Corners Units 4 and 5	7.0%	188		4		(81)		111
Luna	33.3%	59		1		(3)		57
Gila River Unit 3	75.0%	206		—		(65)		141
Gila River Common Facilities	43.8%	75		1		(26)		50
Springerville Coal Handling Facilities	83.0%	209		—		(95)		114
Springerville Common Facilities	86.0%	399		—		(207)		192
Transmission Facilities	Various	462		20		(229)		253
Total		$	1,883	$	27	$	(975)	$	935

Schedule of asset retirement obligations

The following table reconciles the beginning and ending aggregate carrying amounts of ARO accruals on the Consolidated Balance Sheets:

	December 31,
(in millions)	2021		2020
Beginning of Period	$	96	$	107
Liabilities Incurred (1)	14		—
Liabilities Settled (2)	(2)		(5)
Regulatory Deferral/Accretion Expense	4		4
Revisions to the Present Value of Estimated Cash Flows (3)	27		(10)
End of Period	$	139	$	96

(1)Asset retirement obligation for Oso Grande, placed in service in May 2021.

(2)Primarily related to the retirement of Navajo.

(3)Primarily related to changes due to revised estimates of the timing of cash flows required to settle future liabilities of San Juan and changes in ownership of Springerville Common Facilities.