This is interesting to me, because I've been advocating for a similar law for a while now, with a few crucial differences:
I propose we make a law that says any home that sells for greater than the Freddie Mac super conforming loan limit (currently $679,650) must be retrofitted to have a net energy draw of zero or less from the grid (with rules about exceptions for shade and roof angles and whatnot).
This would solve a lot of problems with this bill: It would exempt all the folks who are selling cheap homes throughout the state, it would apply to both old and new homes, and it allows for new technologies that don't exist yet or are cost prohibitive, instead of require solar panels.
It wouldn't really affect prices much, because there is already a flattening at the Freddie Mac limits, and when you get to the super conforming level, a solar install only represents 5% or less today (but I imagine the prices would fall with economies of scale).