There is a company in Colorado that sells solar equipment for 60 cents a watt, installation extra. Here in Yuma, AZ one company is advertising an average cost of $3.75 per watt installed. Feel free to compare prices in Cali to those figures.
They should really have checked out Germany's issues before mandating this for all new housing.
From what I read? They range from $2.84 to $3.62 with the average being about $3.23.
It doesn't start being mandatory till 2020.
So estimating three bux per watt and 10 kilowatts for an average home, we get a price increase of 30 kilobucks ON EVERY NEW HOME. As the market works, that means a price increase on older homes too, just because.
Oh, and 10 kw is only the peak power. You have to have a battery bank to get power the rest of the day. I have not estimated the cost of batteries but they ain't cheap. New types of batteries are being invented, but they are kinda unlikely to reach the market as long as buyers have no choice.
(If you feel like studying that, you can search "iron chloride battery".)