| a measure of the efficiency of a heating or cooling system, as a heat pump or air conditioner, equal to the ratio of the output in B.T.U./hour to the input in watts: A high-efficiency home window air conditioner has an energy efficiency ratio of 7.5 or more. Abbreviation: EER |
| energy efficiency ratio n. A measure of the relative efficiency of a heating or cooling appliance, such as an air conditioner, that is equal to the unit's output in BTUs per hour divided by its consumption of energy, measured in watts. |