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 posts What is the difference between SEER and SEER2? and How can I find out the SEER of my air conditioner?

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.