I'm sure that our last gas tax was put in place in the anticipation of more electric vehicles on the roads. For the time being, they have no way to gather road use money from a "home charged" vehicle. A Tesla puts the same stresses on a highway that a 300 does.
California needs to reduce the tax on Gas and diesel, and start taxing on miles driven per year. Collected by the DMV at registration time, IMO. Of course that asks the question, what about the out of state vehicles driving on our roads?