We don't use our air conditioner or our heater because the costs are just too high. When we do use them, the bill ranges from $350 to $700 a month! Who in the world can afford that? Not me. We have found ways to keep the house cool. We are in California and the temps range from 90 to over 100. We were actually happy that it was getting down to 90s recently!
If you live in a safe enough neighborhood, open up doors and windows (with screens) early in the morning and turn on fans. Then when it gets hot, we close windows that are no longer bringing in a breeze (if it is hot outside the window or door, close it). Fans move air around and make the house feel cooler and they are less expensive. So we use ceiling fans. Then when it gets hotter I tie a wet bandana around my neck and sleep with an ice pack. We have a pool, but it it being repaired and taking a long time. Hopefully we can get in the pool soon to cool off.
I've also heard that a whole house fan is good for cooling the house off in the morning. It takes the hot air out through the roof or something like that. Probably not cost effective for our northern folks, but we thought about getting one.