The cost of running our air conditioners is included in our rent so we can set them as cold as we want and not worry about outrageous electricity bills. We, of course, don't run it when we're not home since we don't want to have to move when the icecaps melt, but I wish I could say all my neighbors felt the same way. I leave it off all day and turn it on high blast when I go to bed. It's uncomfortably hot for a bit, then I usually wake up in the middle of the night and I swear I'd be able to see my breath if the lights were on. But if I leave it on SmartFan it manages to shift speeds just as I'm falling asleep, and it sounds like the transmission fell out of the bottom of a semi-truck. So, I run it at high all night, perhaps causing a bit of the world to warm, but don't worry, that's how I sleep at night.