The last 2 places we have owned only had window air. Guys had told me with a window air unit, it needs to be shut off at night so the unit won't overheat. But now, my new place has central air. I am not mecahanically inclined, but people with central air seem to keep theirs running all the time during the heat and humidity streaks. Is that, I would suppose, because if you shut it off, it takes more power to get it back to where it was. I just can't understand that concept, and don't want to be wasting power. I dad one neighbor when I lived in town who went straight from furnace season to air season, only because their house didn't come with screen windows. Me, I enjoy having the windows open.