Your central air-conditioning system needs to work at its best in the hottest weather. Here are some tips to get more savings and comfort out of your air conditioning.
Block sunlight. The sun's heat can increase the indoor temperature significantly, said Harvey Sachs of the non-profit American Council for an Energy-Efficient Economy in Washington.
Close window coverings on the sunny sides of the house during the day, Sachs said. Longer term, consider adding awnings or planting trees for shade.
Leave it on. People sometimes turn the central air conditioning on only at night to save money. That's fine when the weather isn't too hot, but it's a bad idea when the temperature reaches 90 or so.
Turning off the A/C in extreme heat lets heat and moisture build up in the house, he said. The unit can't eliminate them quickly enough to make the house comfortable at night, and it uses a lot of electricity trying.
Clear the condenser. The outdoor condensing unit needs a supply of outside air to blow across the heated refrigerant. Make sure the condenser has enough space around it to permit good air flow. Trim plants that are growing close to the unit, and make sure no mulch, grass or debris is blocking the bottom openings.
Energy auditor Karl Bella recommends a clearance of at least 8 inches all around.
Check the air filter. In almost every forced-air system, the furnace filter also is the air-conditioning filter. A clogged filter reduces air flow. Change or clean it as often as the manufacturer recommends, usually every one to three months.
Set the fan on automatic. Conventional wisdom used to dictate running the fan on an air-conditioning system constantly to keep air moving throughout the house. Newer research suggests otherwise, Bella said.
Leaving the fan running increases the stack effect, a house's tendency to draw outside air to replace air that rises and escapes through openings high in the building. The more hot outside air comes in, the harder the air conditioner has to work, he said.
Sachs said that when the fan runs non-stop, the moving air picks up moisture from the saturated coils when the compressor isn't running. That defeats the unit's purpose of drying the air.
Mind the registers. Central air conditioning works best if air can flow through the house freely. Make sure nothing is blocking supply registers or cold-air returns, Bella said.
Don't be tempted to block air returns. It might seem logical that they'll keep the cooled air in a room, but they just keep the air from returning to the central unit.
Be careful when closing supply registers in unoccupied rooms. Overdoing it un balances air flow throughout the house and results in cool and hot spots, the American Council for an Energy- Efficient Economy says.
Leave the oven off. Even when closed, a hot oven adds as much heat to the air as an air conditioner can take out in the same amount of time, Foraker said. Try not to cook indoors on the hottest days.
Turn out the lights. Incandescent light bulbs turn only 10 percent of electricity into light. The rest becomes heat. Turn off unneeded lights or switch to cooler compact fluorescent bulbs.
Use ceiling fans. A ceiling fan moves air over the skin, evaporating perspiration and making you feel cooler. Running one even when the air conditioning is on will increase your comfort.
The fans also help move air around the room, but it's not enough of a benefit to justify leaving a ceiling fan on in an unoccupied room, the Alliance to Save Energy says.
Minimize humidity. Don't add more moisture to the air than is necessary. Run exhaust fans when you shower, and run hot-water appliances — dishwashers and clothes washers —in the evening, the American Council for an Energy-Efficient Economy recommends.
Check the duct dampers. In a house with more than one floor, adjusting the balancing dampers helps to send the cool air where you want it.
A damper is essentially a little door in the duct that directs more or less air to a particular part of the house. A lever on the outside of the duct controls the damper.
Look for the dampers in the supply ducts somewhere near the furnace.
In winter, you want to direct most of the heated air to the lower level, because warm air rises. In summer, you want to direct most of the cool air to the upper level.
Once you find those positions, mark them with a W for winter and an S for summer. You might even note in your calender to change the dampers in spring and fall.