Tesla’s biggest windfall has been the cash payments it extracts from rival car makers (and their customers), via its sale of zero-emission credits. A number of states including California require that traditional car makers reach certain production quotas of zero-emission vehicles—or to purchase credits if they cannot. Tesla is a main supplier. Take away the credits and Tesla lost $53 million in the first quarter, or $10,000 per car sold. California’s zero-emission credits provided $67.9 million to the company in the first quarter, and the combination of that state’s credits and federal and local incentives can add up to $45,000 per Tesla sold, according to an analysis by the Los Angeles Times. A Morgan Stanley MS +1.40% report in April said Tesla made $40.5 million on credits in 2012, and that it could collect $250 million in 2013. Tesla acknowledged in a recent SEC filing that emissions credit sales hit $85 million in 2013’s first quarter alone—15% of its revenue, and the only reason it made a profit.