Efficient to AC both upstairs and down?
We have two AC units (one each for up and downstairs). We don't use our upstairs in the summer. Is it more efficient to turn off the upstairs, or does that make the downstairs unit work harder? Our foyer goes up to the second floor ceiling. We can close off the rooms upstairs but not the hall and of course, foyer area. Does it make more monetary sense to cool the upstairs just a bit so the downstairs AC doesn't work so hard? Thanks.