Tesla is not the only automaker that makes money selling California zero-emission vehicle (ZEV) credits (Nissan has joined the party) but it does sell more of them than anyone else. That's the word from BusinessWeek, which says the California-based automaker sold 1,311.52 ZEV credits between October 1, 2012, and September 30, 2013. BusinessWeek says that the second-highest seller of credits generated by ZEVs was Suzuki, with 41.199.
But let's clarify that a bit. The general idea of the ZEV credits is that "large" and "intermediate" automakers who sell cars in California (see the list here) have to make a certain percentage of ZEVs (the number gets bigger over the years) and, if they don't make enough cars, they can buy credits from companies who make "too many." It's not as simple as one electric vehicle equals one credit (a Tesla Model S can be worth up to seven, for example) and the credits are a confusing number based on "units of grams per mile Non-Methane Organic Gases (g/mi NMOG)." Seriously. There's more information here (PDF).
Anyway, Toyota actually sold more ZEV credits last year - 507.5 - than Suzuki did but those were generated from sales of Toyota's Advanced Technology Partial-ZEV vehicles (i.e., the Toyota Prius Plug-In). Nissan sold 25 PZEV credits. And if you're wondering what vehicle it was that Suzuki was offering, we're actually not sure, but we do know that automakers can bank credits for years and the CARB ZEV program started in 1990. The biggest buyer of ZEV credits was General Motors, with ZEV a total of 876.365 (that's 368.865 ZEV and 507.50 AT PZEV), followed by Chrysler with 551.197 (526.197 ZEV and 25 PZEV).
CARB won't say how much the ZEV credits go for since they're traded privately between companies, but CARB spokesman Dave Clegern told BusinessWeek that all of the automakers involved in the program are "in compliance and that to us is the goal."