I did some napkin calculations years back and came to the conclusion that solar cells would have to be about 80% efficient to really be cost-effective. (Initial price, maintenance, cell-lifetime, etc.)
It's probably a little on the high side.
The funny thing is that if everyone starts installing solar power the pricing will come down on everything related including batteries. Once that happens solar could actually be a viable replacement for grid power. What then would the fedscum and greens do to stop it?
The same thing they always do: add more regulations.
Probably requiring certified technicians to do any work at all on them, at the very least.