Air Conditioner EER, CEER, and SEER Rating
EER (Energy Efficiency Ratio) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level. The higher the EER, the more efficient the system. It is calculated by dividing the cooling capacity in BTUs per hour (BTUH) by the power input in watts. EER is expressed as BTUH/watts.
CEER (Combined Energy Efficiency Ratio) is the new standard by which Window Air conditioners are rated by the DOE (Department of Energy), as of June 2014. It takes in account the energy used while the air conditioner is running, as well as the standby power used when the unit is not running but is powered on.
SEER (Seasonal Energy Efficiency Ratio) is most commonly used to measure the efficiency of a central air conditioner. SEER measures how efficiently a cooling system will operate over an entire season. The higher the SEER, the more efficient the system.
The EER and/or CEER rating is listed in the model's product details. Room air conditioners do not have SEER ratings.