Early Plant Retirements (Tables)

12 Months Ended

Dec. 31, 2020

Implications of Potential Early Plant Retirements [Abstract]

Restructuring and Related Costs [Table Text Block]

As a result of the decision to early retire Byron and Dresden, Exelon and Generation recognized certain one-time charges for the year ended December 31, 2020 related to materials and supplies inventory reserve adjustments, employee-related costs, including severance benefit costs further discussed below, and construction work-in-progress impairments, among other items. In addition, as a result of the decisions to early retire Byron and Dresden, there are ongoing annual financial impacts stemming from shortening the expected economic useful lives of these nuclear plants primarily related to accelerated depreciation of plant assets (including any ARC), accelerated amortization of nuclear fuel, and changes in ARO accretion expense associated with the changes in decommissioning timing and cost assumptions to reflect an earlier retirement date. See Note 10 — Asset Retirement Obligations for additional information on changes to the nuclear decommissioning ARO balance and Note 12 — Asset Impairments for impairment assessment considerations given to the Midwest asset group as a result of the early retirement decision. The total impact on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income is summarized in the table below.

Income statement expense (pre-tax)	2020(a)		2019(b)		2018(c)
Depreciation and amortization
Accelerated depreciation(d)	$	895	$	216	$	539
Accelerated nuclear fuel amortization	60		13		57
Operating and maintenance
One-time charges	255		—		32
Other charges(e)	34		(53)		—
Contractual offset(f)	(364)		—		—
Total	$	880	$	176	$	628

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(a)Reflects expense for Byron and Dresden.

(b)Reflects expense for TMI.

(c)Reflects expense for TMI and Oyster Creek.

(d)Includes the accelerated depreciation of plant assets including any ARC.

(e)For Dresden, reflects the net impacts associated with the remeasurement of the ARO. For TMI, primarily reflects the net impacts associated with the remeasurement of the ARO. See Note 10 - Asset Retirement Obligations for additional information.

(f)Reflects contractual offset for ARO accretion, ARC depreciation, and net impacts associated with the remeasurement of the ARO. For Byron and Dresden, based on the regulatory agreement with the ICC, decommissioning-related activities in 2020 have been offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset in 2020 resulted in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 10 - Asset Retirement Obligations for additional information.

Implications of Potential Early Plant Retirement on Balance Sheet [Table Text Block]

The following table provides the balance sheet amounts as of December 31, 2020 for Exelon's and Generation's significant assets and liabilities associated with the Braidwood and LaSalle nuclear plants. Current depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses.

	Braidwood		LaSalle		Total
Asset Balances
Materials and supplies inventory, net	$	84	$	106	$	190
Nuclear fuel inventory, net	120		285		405
Completed plant, net	1,397		1,590		2,987
Construction work in progress	31		30		61
Liability Balances
Asset retirement obligation	(570)		(954)		(1,524)
NRC License First Renewal Term	2046 (Unit 1)		2042 (Unit 1)
	2047 (Unit 2)		2043 (Unit 2)