My wife and I live in the same condo I used to live in as a bachelor. My frugal single self saw the electric bill for heating and AC around $50/month. I would only use the heating or AC for an hour or two when I got back from work, which would be enough to heat or cool the apartment until morning.

After we got married and my wife moved in, we use the heat a lot, lot more since she can't stand the cold (she's fine without the AC - even more so than me). The electric bill during the peak winter months easily balloons to $300-400 now.