What is the difference between the SEER and EER rating of an air conditioner?
Friday, August 10, 2018
The Seasonal Energy Efficiency Ratio (SEER) is an evaluation of the energy usage over a typical cooling season, based on a constant indoor temperature of 80º F and varying outdoor temperature of between 65º and 104º F. It is a ratio of output cooling energy in BTU’s (British Thermal Units, a measure of heat production) to input electrical energy in watt-hours (one watt of electricity for duration of one hour). Because it is a ratio, there is no unit of measurement attached to it.
The difference between SEER and EER (Energy Efficiency Ratio) is that EER is an evaluation of the operating efficiency at the same indoor temperature setting of 80º F, but with a constant 95º F outdoor temperature.
The SEER rating is stated on the stickers on the outdoor (condenser) unit of an HVAC system, and a higher SEER means a more energy-saving system. Changing out a 15-year old system with at SEER of 10 to a new system with the current minimum SEER allowed by the U.S. Department of Energy of 14 would reduce your energy consumption by about 30% (the calculation is 1 minus 10/14).
Basically, SEER more accurately states the operating efficiency over variable weather, while EER expresses the efficiency at one operating condition. Because EER is based on a more difficult scenario, it is a lower number and typically about 0.875 of SEER. So a heat pump or cooling air conditioner with a SEER of 15 would have an EER of around 13.
Also, see our blog post How can I find out the SEER of my air conditioner?
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