[ggm]

Solar. Wind. The mcguffin to get electricity is lower bar post apocalypse than oil, given even current levels of deployment.

Replacement is harder, because polycrystalline manufacture depends on unbelievably precise doping of nine nines or better pure silicon. Digging oil up is probably easier but you can run a turbine on any combustible gas, even powdered coal at a pinch. So set the survivalists in Seattle and rob the Boeing factory of jet engines to run the generators.