I don't have any data on this, but anecdotally it seems like most residential buildings in San Diego built before ~1980 don't even have AC. The same goes for Lo

I don't have any data on this, but anecdotally it seems like most residential buildings in San Diego built before ~1980 don't even have AC. The same goes for Los Angeles and San Francisco. Heaters are required but you'll almost never use them.