Use Your Windows to Gain Cool Air and Keep Out Heat
If you live in a climate where it cools off at night, turn off your cooling system and open your windows while sleeping. When you wake in the morning, shut the windows and blinds to capture the cool air.
Operate Your Thermostat Efficiently
Set your thermostat as high as comfortably possible in the summer. The smaller the difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be.
Keep your house warmer than normal when you are away, and lower the thermostat setting to 78°F (26°C) only when you are at home and need cooling. A programmable thermostat can make it easy to set back your temperature.