UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Tables)

12 Months Ended

Dec. 31, 2023

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)			2023		2022
Plant in Service
Generation Plant	3.05%	22	$	3,536	$	3,491
Distribution Plant	2.61%	46	2,279		2,149
Transmission Plant	1.69%	33	1,323		1,295
General Plant	6.13%	9	685		653
Intangible Plant, Software Costs, and Other (1)	Various	Various	201		224
Plant Held for Future Use	—	—	11		2
Total Plant in Service (2)			$	8,035	$	7,814

(1)Primarily represents computer software, which is being 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 as of December 31, 2023 and 2022.

(3)Based on the 2022 depreciation study available for the major classes of Plant in Service, effective September 1, 2023 as approved by the ACC as part of the 2023 Rate Order. TEP implemented new depreciation rates for Transmission Plant based on the 2018 depreciation study, effective August 1, 2019, as approved as part of the 2022 Final FERC Rate Order.

Schedule Of Jointly Owned Utility Plants

As of December 31, 2023, 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
Four Corners Units 4 and 5	7.0%	$	201	$	4	$	(97)	$	108
Luna	33.3%	58		3		—		61
Gila River Unit 3	75.0%	218		17		(62)		173
Gila River Common Facilities	43.8%	78		1		(30)		49
Springerville Coal Handling Facilities	83.0%	208		—		(103)		105
Springerville Common Facilities	86.0%	400		—		(228)		172
Transmission Facilities	Various	555		21		(236)		340
Total		$	1,718	$	46	$	(756)	$	1,008

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)	2023		2022
Beginning of Period	$	121	$	139
Liabilities Incurred (1)	—		1
Liabilities Settled (2)	(2)		(8)
Regulatory Deferral/Accretion Expense	3		5
Revisions to the Present Value of Estimated Cash Flows (3)	(8)		(16)
End of Period	$	114	$	121

(1)In 2022, TEP incurred an ARO for new photovoltaic generation placed in service.

(2)Primarily related to the retirement of Navajo and San Juan.

(3)Primarily related to revised decommissioning estimates for San Juan.