[pyoung]

There is no guarantee that battery costs will come down naturally. The point of the subsidy is to help drive demand long enough so that the market forces have time to work on bringing those costs down. And even then, there is no guarantee that this will work. But batteries are a critical technology for many reasons (particularly the grid), so it makes sense to target this technology specifically. Look at what the CSI program did to CA's solar industry for an example of how fast a well planned incentive program can bootstrap an industry.

Also, CA already has a cap and trade program (a bill just passed to extend the program another 10 years). It has been around since 2012.