Energy-Efficient Air Conditioners for Homes

Measurements of Energy Efficiency

• The Energy Star program expresses appliance efficiency ratings in an energy-efficiency ratio, or EER. This correlates the amount of electric power expressed in watts required to produce cooling, measured in terms of British thermal units, or Btus. The higher the EER, the more efficiently the machine uses power to produce cooling. High EERs run between 8 and 10. High-rated units can be expected to save anywhere from 10 to 30 percent of energy costs over an unrated unit. The EER is a ratio, not a static rating; it does not rate the amount of electric power used to run one unit as opposed to another, nor can it be used to compare the power costs of operating two different units.

Additional Standards

• EERs are used to rate room air conditioners; a second rating is conducted for central air conditioning units: the seasonal energy-efficiency rating, or SEER. The SEER is derived from a series of measurements taken throughout the cooling season and gives an overall view of performance efficiency. Again, the higher the rating, the more efficient and overall less costly the unit.

Maximizing Efficiency

• The most important factor in maximizing air conditioning efficiency is choosing the correct size of unit for the space to be cooled. Very roughly, you should calculate 1 Btu per square foot of space. Making exact and thorough measurements of the whole space to be cooled is your best assurance of getting the most efficient unit for your space.

Impediments to Efficiency

• The greatest impediment to an air conditioner's maximum efficiency may be its owner. Choose a location out of intense sun or strong winds to improve operation. Evaluate and upgrade both insulation and ventilation throughout the house to remove as much hot air by passive means as possible without permitting cold-air leakage. Use less expensive mechanical means, like fans, to cool areas that do not absolutely require air conditioning for comfort. Keep physical barriers, like furniture, and heat sources, like large entertainment units, away from air conditioners to improve functioning. Clean units thoroughly at the beginning of the cooling season and monthly throughout. All of these steps enable you to get the most efficient operation out of your energy-efficient air conditioner.