Improving Air Conditioning Efficiency

Improving Air Conditioning EfficiencyLast November, the U.S. Department of Energy (DOE) announced that it was planning to raise minimum efficiency standards for home central air conditioners and heat pumps. The current air conditioner standard is a seasonal energy efficiency rating (SEER) of 10. The new standards are likely to range from 11 to 13 SEER. The higher standards would represent an increase in efficiency of 10%-30% over today's central air conditioners. What the final standards will be, and the effective date for implementing them, was still up for negotiation at press time.

Meanwhile, in Europe, where until recently cooling needs have been met largely through a building's architectural features, sales of room air conditioners have been growing by 12% annually since 1996. Energy consumption in Europe from room air conditioners reached 12 TWh in 1996, but this usage is projected to climb to more than 44 TWh per year by 2020 under a business-as-usual scenario. A recent European Union study recommended the imposition of two tiers of minimum energy efficiency standards for room air conditioners to help contain the rising electricity consumption of these appliances. The first tier would be implemented in 2003; the second by 2010 at the latest. The technical changes needed to improve the efficiency of room air conditioners are well understood (see ).
--Mary James

Mary James is editor/publisher of Home Energy.

For more information:For more information on the standards, see the DOE Web site at: Or, call (202)586-5806.
Table 1. Methods for Improving the Energy Efficiency of Room Air Conditioners

Technological Improvements
Increase in Energy Efficiency Ratio*

30% increase in frontal coil (heat exchanger) area

45% increase in frontal coil (heat exchanger) area

Addition of one extra row of refrigerant tubing in frontal coil

Addition of two extra rows of refrigerant tubing in frontal coil

20% increase in coil fin density

Improved coil fin design (modified fin pattern)

Improved refrigerant tubing heat transfer

15% more efficient compressor

Use of variable speed compressor

Source: "Hungry Cooling: Room Air-Conditioners," Appliance Efficiency 3, no. 3, (1999) p. 6-10.
*Energy Efficiency Ratio = cooling capacity of air conditioner in watts/electrical input power in watts