Taxpayers usually have a vote on whether or not specific taxes are approved for initiatives like this at the local level. And voters have some way to affect their representatives that push for specific policies at the state level. Rate payers are asked to pay whenever the CPUC authorizes stuff that never goes to a vote. And I think all CPUC leaders are appointed or internally hired; not voted upon.
Also remember, some NEM customers aren't paying rates at all since they are basking in the glory of their mega solar arrays and only paying nominal NBCs (which do not include costs for programs such as SGIP). There is no convenient way to evade stuff that gets funded by a sales tax, excise tax, property tax, etc.
@h2ofun is a taxpayer, but he isn't a ratepayer any more (for the next 19 years... then he'll have to become a ratepayer again).
But yeah I agree in general. Someone who gets an SGIP Battery is benefitting from others who aren't paying. Just like the bazillions of other public goods that benefit some but are paid for by all. Cost shifts FTW and FTL.