Permitting in California more than doubles the installation cost of home batteries + PG&E gets to screw with you if you buy one.

Propane generators here have the same problem.

That still doesn't explain the price gap. You can literally just get a V2H EV and use it instead of a home battery (or, you could if the ecosystem was more mature).

If it's wired to the grid I presume. So if it's just for emergencies, don't wire it to the grid.