I think also that, although the lighting may often be on in empty offices, the computers (and body heat) are lower, or missing entirely, so the offices aren't h

I think also that, although the lighting may often be on in empty offices, the computers (and body heat) are lower, or missing entirely, so the offices aren't having to work very hard. However, all that load has shifted back to WFH, not gone away, so now the same amount of heat is being handled by less efficient A/Cs, in smaller buildings. All speculative, though, and probably not the main driver, I admit.