That isn't even the major electrical cost of supporting those people. The fertilizer needed to feed them, metal refining/recycling, chemical reagent production, shipping fuel, all dwarf the usage by individuals in their homes.

Personally I don't think solar is ever feasible for industrial scale work, covering like 1/3 of your landmass is a ridiculously large project and needed to fuel industrial operations that currently use fossil fuels to fuel them including fertilizer production. Even if you can shrink that down a bit, how much of it is competing for farmland? Or replacing natural forests or plains or other wildlife housing.