Give AC a rest when you're away for even a few hours. Set programmable thermostats to kick in half an hour before you return home unless you have heat-sensitive indoor pets. Cranking the thermostat to penguin-worthy temperatures won't cool the house faster, since AC works at full throttle until a set temperature is reached. With every degree you lower it, cooling costs increase by about 7 percent.

Give small appliances a break whenever you can. Computers, cell phone chargers, and other electronics often continue to use power -- and radiate heat -- even when turned off. To simplify, plug items into a power strip that you can use as a master switch.

Incandescent bulbs put more energy into generating heat than light, so replace high-use bulbs with compact fluorescent lightbulbs (CFLs). They burn cool and bright with only a third of the power required by incandescents.

Position a fan to blow air out a window. Close nearby windows to keep the hot air from flowing back in and open those on the other side of the house (ideally in cool, shaded areas). In a multilevel home, place the fan in a top-floor window and open windows on lower floors, where air is cooler.

If you have central AC, schedule annual servicing. Visits can be costly, but repairs and tune-ups that increase efficiency soon pay for themselves. You stand to earn significant savings by replacing a system sold in the 1990s, which can guzzle up to 40 percent more energy than today's most efficient systems.

Run appliances such as clothes dryers and dishwashers at night to avoid peak energy rates and the humid heat they generate. Excess humidity is more than uncomfortable -- it can also be expensive, since air conditioners use extra energy to process the moisture.

Take advantage of summer weather and cook outdoors, as prolonged baking or stovetop cooking makes AC work overtime. Too muggy outside? Use a microwave or toaster oven, which use less energy and generate less heat. When you need to use a burner, keep pots covered to cook food faster and minimize humid heat in the kitchen.

Don't keep extra refrigerators and freezers in unconditioned spaces, such as garages, where heat tends to build up. Save more energy by opting for a chest freezer, which loses less cold air when opened. Keep all freezers relatively full for maximum efficiency.

About 90 percent of the energy used for a load of laundry goes to heating the water. Some stains demand hot water, as do bed linens (to kill dust mites). Wash all other loads in cold.

Single- and even some double-pane clear glass windows can force heating and cooling systems to work overtime. Energy Star-qualified windows with insulating glazes, gas fills, and better framing materials deliver the best results. For an extra boost, use blackout blinds or heavy drapes to minimize solar heat gain to cover windows that catch direct sun.