Our solar energy systems, net, consisted of the following (in millions):


	December 31,			December 31,
	2021			2020
Solar energy systems in service	$	6,809		$	6,758
Initial direct costs related to customer solar energy system lease acquisition costs		104			103
		6,913			6,861
Less: accumulated depreciation and amortization (1)		(1,187	)		(955	)
		5,726			5,906
Solar energy systems under construction		18			28
Solar energy systems pending interconnection		21			45
Solar energy systems, net (2) (3)	$	5,765		$	5,979

(1)

Depreciation and amortization expense during the years ended December 31, 2021, 2020 and 2019 was $236 million, $232 million and $227 million, respectively.

(2)

As of December 31, 2021 and 2020, solar energy systems, net, included $36 million of gross finance leased assets with accumulated depreciation and amortization of $9 million and $7 million, respectively.

(3)

As of December 31, 2021 and 2020, there were $1.02 billion and $1.05 billion, respectively, of gross solar energy systems under lease pass-through fund arrangements with accumulated depreciation of $165 million and $137 million, respectively.