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, 2018 (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, 2017	16,268		$	5.70	7.41	$	14,832
Granted	1,188		8.05
Exercised	(443	)	4.38
Cancelled / forfeited	(184	)	8.30
Outstanding at March 31, 2018	16,829		$	5.87	7.39	$	53,592

Options vested and exercisable at March 31, 2018	8,964		$	5.55	6.18	$	31,957

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, 2018 (shares in thousands):



	Number of Awards		Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2017	5,330		$	5.82
Granted	1,452		7.77
Issued	(888	)	6.93
Cancelled / forfeited	(406	)	5.41
Unvested balance at March 31, 2018	5,488		$	6.19

Employee Stock Purchase Plan

Under the Company's amended 2015 Employee Stock Purchase Plan ("ESPP"), eligible employees are offered shares bi-annually through a 24 month offering period which 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,
	2018		2017
Cost of customer agreements and incentives	$	611	$	751
Cost of solar energy systems and product sales	170		114
Sales and marketing	4,150		1,917
Research and development	295		149
General and administration	5,468		2,943
Total	$	10,694	$	5,874

In August 2017, the Company entered into an agreement with an affiliate ("Contractor") of Comcast Corporation ("Comcast") whereby Contractor will receive lead or sales fees for new customers it brings to the Company over a 40-month term. The Company also issued Comcast a warrant to purchase up to 11,793,355 shares of the Company's common stock, at an exercise price of $0.01 per warrant share. The warrant initially vests 50.05% when both (i) Contractor has earned a lead or sales fee with respect to 30,000 of installed solar energy systems, and (ii) Contractor or its affiliates have spent at least $10.0 million in marketing and sales in connection with the agreement. Thereafter, the warrant will vest in five additional increments for each additional 6,000 installed solar energy systems.