What is SEER?

The North American AHRI rates air conditioner efficiency by the Seasonal Energy Efficiency Ratio (SEER). Speaking simply, a SEER rating is a measure of how efficiently a system will use electricity to produce cooling output during a typical cooling-season. The higher the SEER the more efficient the unit. Energy efficient heat pumps and conventional air conditioners are rated by SEER.

What is EER?

Energy Efficiency Ratio (EER) and SEER are very similar. Both ratings measure cooling output to energy input, but EER assumes stable environmental conditions instead of accounting for seasonal temperature fluctuations. Geothermal heat pumps are rated by EER instead of SEER, since geothermal units rely on a stable subsurface environment as a basic part of their operating cycle.

Which is Better?

The two rating systems are not identical, and one is not better than the other. They are used merely to describe different systems that do a similar job. EER is the efficiency you can expect from the air conditioner at peak cooling time (in the midst of the summer) because it is measured at only one, higher temperature. SEER is an average. It takes into account the highs and lows of a typical home’s cooling pattern. For areas of the country where it is 95°F or higher most of the time the air conditioner is on, the EER is usually more accurate. For more moderate climates like Southern California, the SEER is a better measurement. When in doubt, remember that geothermal heat pumps use EER and air conditioners use SEER. If you want to convert between the two without doing a lot of math, refer to our conversion chart here.