I'm thinking it must take quite a bit more energy to heat all those big sprawling Texas homes to a comfortable temp during the day than the relative efficiency

I'm thinking it must take quite a bit more energy to heat all those big sprawling Texas homes to a comfortable temp during the day than the relative efficiency you can get for heating a building full of tightly packed offices. But this would be more of an issue with cooling since it is hotter mid-day. Whereas with cold, it gets colder at night, and most people are at home at night anyway.