And decreases the energy bill by a very similar amount of what an increase in the mortgage would be if the cost was 100% passed on. Regardless, in much of California the price of homes has little to do with the cost of building them. So another possibility is buildable land gets a little cheaper because building is more expensive and homes are priced by what the market will bear, not by material cost.
Let us assume that there is simply a hardware expense because the builders already have roofers and electricians. It’s such a fraction of a mouse fart (as mentioned) that going solar will essentially pay for itself after 2 years.
I can see builders charging a premium for the "electric car package" or the "double your consumption" service but something like 3W of production for each square foot per month would be amazing.
Sure, this is true iff a) the home has a nice south-facing roof, b) without trees in the way and c) under the current tariff design in most of California.
Some homes are built in wooded areas. Deciduous trees on the south side of the house (in the northern hemisphere) 1) shade in the summer, 2) allow the sun to warm in the winter are 3) are attractive.
Finally, regulated-monopoly utilities will continue to pass their costs to their customers. They will change the designs of their rates to continue to recoup their costs. So what might be saved in utilities costs today won't necessarily be saved over the life of the mortgage.