If you have central air, set your thermostat above 78 degrees (all temperatures cited here are in degrees Fahrenheit). You'll save 5 to 8 percent on cooling costs with each degree above that mark. For a typical household, setting the thermostat at 80 degrees saves 10 to 15 percent; raising it to 85 degrees will save 35 to 55 percent.
When you leave home for more than one hour, set the thermostat to 85 or 90 degrees. Reset it upon your return, and the room will cool down in only 15 minutes. The system will use less energy during the cool-down period than if you had left it running at a lower setting while you were out.
Typical air-conditioning settings for a programmable thermostat at different times of day:
6 a.m. to 9 a.m. = 75 degrees
9 a.m. to 5:30 p.m. = 85-90 degrees
5:30 p.m. to 11 p.m. = 75 degrees
11 p.m. to 6 a.m. = 80 degrees
Benefit: 15 to 20 percent or more off your cooling bill