Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of components and classification of stock-based compensation expense

The components and classification of stock-based compensation expense, excluding the Company’s matching contributions to the Plug Power Inc. 401(k) Savings & Retirement Plan and quarterly Board compensation, were as follows (in thousands):

	Year ended December 31,
	2023		2022		2021
Cost of sales	$	11,079	$	7,259	$	1,965
Research and development		9,532		6,369		5,983
Selling, general and administrative		129,387		156,127		64,443
	$	149,998	$	169,755	$	72,391

Nonvested Restricted Stock Shares Activity

A summary of restricted common stock and restricted stock unit activity for the year ended December 31, 2023 is as follows (in thousands except share amounts):

		Weighted		Aggregate
		Average Grant Date		Intrinsic
	Shares	Fair Value		Value
Unvested restricted stock at December 31, 2022	6,276,376	$	21.56	$	77,639
Granted	4,131,193		11.55		—
Vested	(2,851,637)		20.40		—
Forfeited	(823,048)		23.60		—
Unvested restricted stock at December 31, 2023	6,732,884	$	15.66	$	30,298

Service Stock Options Awards

Assumptions made for the purpose of estimating fair value

	December 31,	December 31,	December 31,
	2023	2022	2021
Expected term of options (years)	5	5	3-5
Risk free interest rate	3.40% - 4.69%	1.26% - 4.34%	0.61% - 1.23%
Volatility	80.02% - 92.55%	73.38% - 85.97%	72.46% - 76.60%

Schedule of Share-based Compensation, Stock Options, Activity

The following table reflects the Service Stock Option activity for the year ended December 31, 2023:

				Weighted
		Weighted		Average
		Average		Remaining		Aggregate
		Exercise		Contractual		Intrinsic
	Shares	Price		Terms		Value
Options outstanding at December 31, 2022	12,078,269	$	14.34		7.57	$	42,835
Options exercisable at December 31, 2022	6,661,969		8.41		6.40		42,182
Options unvested at December 31, 2022	5,416,300		21.63		9.01		653
Granted	6,849,689		7.08		—		—
Exercised	(716,581)		2.25		—		—
Forfeited	(875,015)		26.27		—		—
Options outstanding at December 31, 2023	17,336,362	$	11.37		7.86	$	11,391
Options exercisable at December 31, 2023	8,288,944		11.84		6.18		7,250
Options unvested at December 31, 2023	9,047,418	$	10.94		9.39	$	4,141

Performance Stock Option Awards

Assumptions made for the purpose of estimating fair value

		December 31,		December 31,		December 31,
		2023		2022		2021
Remaining VWAP performance period (years)		3		3		3
Risk- free interest rate		3.60%		3.10%		1.12%
Expected volatility		75.00%		75.00%		70.00%
Closing stock price on grant date	$	7.87	$	26.38	$	26.92

Schedule of Share-based Compensation, Stock Options, Activity

The following table reflects the Performance Stock Option activity for the year ended December 31, 2023. Solely for the purposes of this table, the number of shares is based on participants earning the maximum number of shares underlying the Performance Stock Options (i.e., 200% of the target number of shares).

				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
	Shares	Price		Terms	Value
Options outstanding at December 31, 2022	15,520,000	$	26.87	5.81	$	—
Options exercisable at December 31, 2022	1,391,000		26.9	5.7		—
Options unvested at December 31, 2022	14,129,000		26.86	5.82		—
Granted	6,405,000		7.87	6.38		—
Exercised	—		—	—		—
Forfeited	—		—	—		—
Options outstanding at December 31, 2023	21,925,000	$	21.32	5.27	$	—
Options exercisable at December 31, 2023	2,782,000		26.92	4.73		—
Options unvested at December 31, 2023	19,143,000	$	20.50	5.35	$	—