Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation

Stock-Based Compensation
3 Months Ended
Mar. 31, 2021
Share-based Payment Arrangement [Abstract]  
Stock-Based Compensation Stock-Based Compensation
Stock Options
The following table summarizes the activity for all stock options under all of the Company’s equity incentive plans for the three months ended March 31, 2021 (shares and aggregate intrinsic value in thousands):
Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value
Outstanding at December 31, 2020 8,019  $ 10.35  6.87 $ 473,371 
Granted 236  53.48 
Exercised (898) 8.81 
Cancelled (172) 10.16 
Outstanding at March 31, 2021 7,185  $ 11.96  6.71 $ 348,628 
Options vested and exercisable at March 31, 2021 4,097  $ 6.81  5.27 $ 219,890 
Restricted Stock Units
The following table summarizes the activity for all restricted stock units (“RSUs”) under all of the Company’s equity incentive plans for the three months ended March 31, 2021 (shares in thousands):
Number of Awards Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2020 7,103  $ 40.17 
Granted 226  63.85 
Issued (1,258) 33.54 
Cancelled / forfeited (196) 20.60 
Unvested balance at March 31, 2021 5,875  $ 43.13 
Warrants for Strategic Partners
During the quarter ended March 31, 2021,the Company issued warrants exercisable for up to 316,177 shares of its common stock to certain strategic partners (calculated using the closing stock price of $60.48 on March 31, 2021) and recognized compensation cost of $1.4 million based on time and performance milestones achieved during the quarter. The exercise price of the warrants is $0.01 per share, and no exercises occurred during the quarter ended March 31, 2021.
Employee Stock Purchase Plan
Under the Company's 2015 Employee Stock Purchase Plan ("ESPP"), eligible employees are offered shares bi-annually through a 24-month offering period that encompasses four six-month purchase periods. Each purchase period begins on the first trading day on or after May 15 and November 15 of each year. Employees may purchase a limited number of shares of the Company’s common stock via regular payroll deductions at a discount of 15% of the lower of the fair market value of the Company’s common stock on the first trading date of each offering period or on the exercise date. Employees may deduct up to 15% of payroll, with a cap of $25,000 of fair market value of shares in any calendar year and 10,000 shares per employee per purchase period.
Stock-Based Compensation Expense
The Company recognized stock-based compensation expense, including ESPP expenses, in the consolidated statements of operations as follows (in thousands):
Three Months Ended March 31,
2021 2020
Cost of customer agreements and incentives $ 2,232  $ 1,946 
Cost of solar energy systems and product sales
1,304  673 
Sales and marketing 27,106  3,478 
Research and development 676  1,075 
General and administration 46,711  11,773 
Total $ 78,029  $ 18,945 
During the three months ended March 31, 2021, stock-based compensation expense capitalized to solar energy systems, net in the Company’s consolidated balance sheet was $2.6 million.