My mom has decided the air conditioner is costing her too much. She moved to a desert a few years ago, without thinking of the extra cost of surviving the heat of Summer. The air conditioner guy told her that if she wanted to save money, she should leave the thermostat set at about 85, then just leave it there. But she didn't follow that advice. Instead she was turning it off completely at night to "save money", then having to cool the whole house down again the next day. She would also decide periodically that 85 was too hot to tolerate, even with all the fans going in the house (and she has ceiling fans in just about every room) and so turn the air down to 70 or so.
Now she has a big bill. So when I visited recently and stayed overnight, I had to open the window in the guest bedroom when I turned in for the night. It tends to cool off significantly when the sun goes down, but without an open window, the heat just stays inside the house. On recent visits, however, I've had to suffer, nearly unable to sleep (I can't sleep when it's real hot) because the air was off, and even though I had the fan going, I had to leave the window closed. The reason was, right outside that window was a bubbling cesspool that stank like a MASSIVE OPEN SEWER (I had caps lock on there accidentally, but I think I'll keep it that way; it matches the magnitude of the stink). Mom's septic tank was in need of serious service, but she'd spend the money to fix it on a massive picture for the living room wall. It was only in the last few weeks that she finally had the tank pumped, so I was able to enjoy the refreshing cool breezes of the nighttime air and actually sleep instead of tossing and turning in a long, dark hellish nightmare.