Why not use clean solar energy?

It's unwise to continue having every structure's entire electricity supply relying on external power lines that are susceptible to being crippled by unforeseen events like storms of unprecedented magnitude.

- Frank Sterle Jnr

It seems logical that every structure should try independently harvesting solar energy, at least as an emergency power storage system.

There already are fossil fuel-powered generator systems that engage once the regular electric grid flow gets cut off, so why not use clean solar energy instead of the very old-school and carbon intensive means?