The efficiency of room air conditioners is measured by the energy efficiency rating (EER), which is the ratio of the cooling output (in Btu) divided by the power consumption (in watt hours). A typical new room air conditioner has an EER of about 10, and to qualify for an Energy Star label requires a EER of 11 or higher.
Central air conditioners and heat pumps operating in the cooling mode are rated according to their seasonal energy efficiency ratio (SEER), which is the seasonal cooling output (in Btu) divided by the seasonal energy input in watt hours for an average U.S. climate. Many older central air conditioners have SEER ratings of only 6 or 7. The average central air conditioner sold in 1998 had a SEER of about 11, and to qualify for an Energy Star label requires a SEER of 13 or higher.
Central air conditioners are usually more efficient than room air conditioners, and in general, large capacity air conditioners have higher efficiency (provided you are not buying a larger system than is needed just because it has high efficiency).
General Cooling Tips
GSA’s Federal Supply Schedules 71 II E and 72 II are for lighting technologies such as lamps, track lighting, shades, etc., and Supply Schedule 539 is for lighting technologies such as light bulbs.
U.S. Department of the Interior
Greening of the Interior