The Company recognized $15.0 million and $9.4 million of stock-based compensation expense for the years ended December 31, 2023 and 2022, respectively. As of December 31, 2023, the Company had $33.6 million of unrecognized stock-based compensation expense related to unvested restricted units, which the Company expects to recognize over a weighted-average remaining period of approximately 2 years.

Prior to the Merger, Legacy Altus maintained the APAM Holdings LLC Restricted Units Plan, adopted in 2015 (the “APAM Plan”) and APAM Holdings LLC adopted the 2021 Profits Interest Incentive Plan (the “Holdings Plan”, and together with the APAM Plan, the “Legacy Incentive Plans”), which provided for the grant of restricted units that were intended to qualify as profits interests to employees, officers, directors and consultants. In connection with the Merger, vested restricted units previously granted under the Legacy Incentive Plans were exchanged for shares of Class A Common Stock, and unvested shares of Legacy Altus common stock under each of the Legacy Incentive Plans were exchanged for restricted Class A Common Stock with the same vesting conditions. During the years ended December 31, 2023 and 2022, 60,549 and zero shares were forfeited under the Holdings Plan. As of December 31, 2023 and 2022, 210,710 and 542,511 shares of Class A Common Stock were restricted under the Holdings Plan, respectively. During the years ended December 31, 2023 and 2022, no shares were granted and no further awards will be made under the Legacy Incentive Plans.

The fair value of the granted units was determined using the Black-Scholes Option Pricing model and relied on assumptions and inputs provided by the Company. All option models utilize the same assumptions with regard to (i) current valuation, (ii) volatility, (iii) risk-free interest rate, and (iv) time to maturity. The models, however, use different assumptions with regard to the strike price which vary by award.

On July 12, 2021, the Company entered into the Management Equity Incentive Letter with each of Mr. Felton and Mr. Norell pursuant to which, on February 5, 2022, the Compensation Committee granted to Mr. Felton and Mr. Norell, together with other senior executives, including Anthony Savino, Chief Construction Officer, and Dustin Weber, Chief Financial Officer, restricted stock units (“RSUs”) under the Omnibus Incentive Plan (the "Incentive Plan") that are subject to time-based and, for the named executive officers and certain other executives, eighty percent (80%) of such RSUs also further subject to performance-based vesting, with respect to an aggregate five percent (5%) of the Company’s Class A common stock on a fully diluted basis, excluding the then-outstanding shares of the Company’s Class B common stock or any shares of the Company’s Class A common stock into which such shares of the Company’s Class B common stock are or may be convertible. Subject to continued employment on each applicable vesting date, the time-based RSUs generally vest 33 1/3% on each of the third, fourth and fifth anniversaries of the Closing, and the performance-based RSUs vest with respect to 33 1/3% of the award upon the achievement of the above time-based requirement and the achievement of a hurdle representing a 25% annual compound annual growth rate measured based on an initial value of $10.00 per share (i.e., on each of the third anniversary, the fourth anniversary, and the fifth anniversary of the date of grant, the stock price performance hurdle shall be $19.53, $24.41, $30.51, respectively).

As of December 31, 2023 and 2022, there were 30,992,545 and 23,047,325 shares of the Company's Class A common stock authorized for issuance under the Incentive Plan, respectively. The number of shares authorized for issuance under the Incentive Plan will increase on January 1 of each year from 2024 to 2031 by the lesser of (i) 5% of the number of shares outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the Company's board of directors. The number of shares authorized for issuance under the Incentive Plan increased by 5% of outstanding shares as described in the foregoing on January 1, 2022, and January 1, 2023.


	Number of RSUs Outstanding	Weighted-Average Grant Date Fair Value Per Share
Balances as of December 31, 2021	—	—
RSUs granted	8,105,539	$	5.27
RSUs forfeited	(65,650)	7.40
Balances as of December 31, 2022	8,039,889	5.25
RSUs granted	3,104,600	5.52
RSUs vested	(154,023)	7.25
RSUs forfeited	(300,655)	5.45
Balances as of December 31, 2023	10,689,811	$	5.29

RSUs granted includes 259,662 RSUs that are subject to market-based vesting conditions, each of which represents the right to receive one share of the Company's Class A Common Stock and which vest in one installment on the third anniversary of the grant date based upon the Company's total stockholder return when compared to the Invesco Solar ETF (“TAN”), subject to certain adjustments, and the Russell 2000 index, assigning a weight of 50% to each.

On December 9, 2021, we adopted the 2021 Employee Stock Purchase Plan ("ESPP"), which provides a means by which eligible employees may be given an opportunity to purchase shares of the Company’s Class A common stock. As of December 31, 2023 and 2022, there were 4,662,020 and 3,072,976 shares of the Company's Class A common stock authorized for issuance under the ESPP, respectively. The number of shares authorized for issuance under the ESPP will increase on January 1 of each year from 2024 to 2031 by the lesser of (i) 1% of the number of shares outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the Company's board of directors. For the years ended December 31, 2023 and 2022, no shares of the Company’s Class A common stock were issued and no stock-based compensation expense was recognized in relation to the ESPP. The number of shares authorized for issuance under the ESPP increased by 1% of outstanding shares as described in the foregoing on January 1, 2022, and January 1, 2023.