, Seasonal Energy Efficient Ration, is “The total heat removed from the conditioned space during the annual cooling season, expressed in BTUs, divided by the total electrical energy consumed by the air conditioner or heat pump during the same season, expressed in watt-hours,” according to the Air-Conditioning Heating and Refrigeration Institute
. Basically it’s the heat removed compared to the energy used in the warm months, a measure of the efficiency of a cooling system. The higher the SEER rating the better the system. To give you some comparison, most window air conditioners have a SEER rating of around 10, and most whole home systems have minimum SEER ratings of 14.