Relatively little energy is actually used for heating and cooling. In the UK, a country pretty far north, it's about a fifth of energy use (https://www.withouthotair.com/c7/page_53.shtml), and could be substantially reduced if heating was actually done using electricity (i.e., with heat pumps, rather than direct heating; heat pumps are available with "efficiency" exceeding 400%, e http://www.withouthotair.com/c21/page_140.shtml, but of course require electricity to run, while most heating today is done by directly burning fuel).

Seasons are definitely not "the biggest obstacle to solar". That would be the night and especially the weather.