Proterra SPAC Presentation Deck

ARCLIGHT TRANSACTION OVERVIEW Detailed Transaction Overview Key Transaction Terms Proterra and ArcLight entered into a business combination agreement on January 11, 2021 ● ArcLight currently has $278MM in cash held in trust account $1.6Bn pro forma enterprise value with strong balance sheet 3.7x 2022E Revenue of $439MM Earn-out of 2% of total shares outstanding at close issued to existing Proterra shareholders at illustrative pro forma share prices of $15.00 and an additional 2.5% at $20.00, $25.00 and $30.00 (or upon a change of control transaction at that valuation) 10% of ArcLight founder shares withheld at close subject to earn-out at $15.00 per share Pro Forma Ownership@ $10.00/Share ArcLight Public Shareholders ArcLight Founder Shares PIPE Investor Shares Existing Proterra Shareholders¹ Total April 8, 2021 Shares (MM) 27.8 6.3 41.5 164.9 240.4 % 11.5% 2.6% 17.3% 68.6% 100.0% $MM $278 63 415 1,649 $2,404 Illustrative Pro Forma Valuation Share Price at Closing Pro Forma Shares Outstanding (MM) Equity Value Debt & Other Liabilities (Q4'20A) Existing Cash (Q4'20A) Plus: Cash to Balance Sheet Enterprise Value 2022E Revenue EV/2022E Revenue Illustrative Sources and Uses Sources ArcLight Cash in Trust Committed PIPE Stock Consideration to Existing Shareholders ArcLight Founder Shares Total Sources Uses Cash to Balance Sheet Stock Consideration to Existing Shareholders Illustrative Fees & Expenses ArcLight Founder Shares Total Uses PROTERRA 1. Amounts presented on this slide assume (1) there are no redemptions from the trust account and (2) the holders of Proterra's 2020 Convertible Notes receive 30.3MM shares for the conversion in full of $200MM principal amount of their notes (interest calculations and conversion of same not included). If not voluntarily converted at the time of the Closing of the business combination, the 2020 Convertible Notes will convert if Proterra's common stock price exceeds -$9.89 per share for 20 consecutive trading days after at least six months following the closing of the business combination. Amounts also exclude (1) outstanding out-of-the-money equity awards and outstanding unvested equity awards rolling over in the transaction and (2) the impact of any equity awards issued at or after the closing of the business combination $10.00 240.4 $2,404 41 (180) (648) $1,617 439 3.7x $MM $278 415 1,649 63 $2,404 $MM $648 1,649 45 63 $2,404 64

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