1. For those with air conditioners, most experts agree that setting the thermostat at 78 degrees when you’re home and between 7 and 10 degrees higher when you’re away for more than two hours will keep your home cool and your power bill down. Also keep in mind that setting your thermostat colder than normal when you first turn it on will not cool your home any faster and could result in added expense, the U.S. Department of Energy says.
2. Ceiling fans are also good for keeping your home comfortably cool. The U.S. Department of Energy recommends turning them off when you leave a room, though, because fans cool people, not rooms. If you are considering installing ceiling fans, make sure the room has a ceiling height of at least 8 feet, and keep in mind that larger blades produce a better effect (think ocean breeze!).
3. Sunblock isn’t just for the beach; you can also (sorta) apply it to your home by remembering to keep your blinds and other window coverings closed during the heat of the day. Installing exterior awnings over large windows can also help, as can weather-stripping around doors and windows or investing in weather-efficient windows.
5. Lastly, before going to bed each night, crack open a few windows (make sure they’re burglar-proofed!) to let in some cool, crisp air.
source: Gilroy Patch