Choosing or Upgrading Your Central Air Conditioner
 

Central air conditioners are more efficient than room air conditioners. In addition, they are out of the way, quiet, and convenient to operate. But to save energy and money, you should try to minimize your use of air conditioning and lower your central air conditioner's energy use. In an average air-conditioned home, air conditioning consumes more than 2000 kilowatt-hours of electricity per year, causing about 3500 pounds of carbon dioxide and 31 pounds of sulfur dioxide to be emitted at the power plant.

If you are considering adding central air conditioning to your home, the deciding factor may be the need for ductwork. If your home has ductwork for a forced-air heating system, you may be able to use it for air distribution. Whether or not your existing ductwork will work for air conditioning depends on its size and your relative heating and cooling loads. Check with a heating and cooling contractor in your area.

If you have an older central air conditioner, consider replacing the outdoor compressor with a modern, high-efficiency unit. Consult a local heating and cooling contractor to ensure that the new compressor is properly matched to the indoor unit.

Proper sizing and installation are key elements in determining air conditioner efficiency. Too large a unit will not adequately remove humidity. Too small a unit will not be able to attain a comfortable temperature on the hottest days. Improper unit location, lack of insulation, and improper duct installation can greatly diminish efficiency.

When buying an air conditioner, look for a model with a high efficiency rating. Central air conditioners are rated according to their seasonal energy efficiency ratio (SEER). SEER indicates the relative amount of energy needed to provide a specific cooling output. Many older systems have SEER ratings of 6 or less. The minimum SEER allowed today is 10 for a split system and 9.7 for a single-package system.