Ratio of realized work or useful output per the amount of supplied effort or energy input. It is used typically as a measure of the energy efficiency. It is the basis for air conditioners, space heaters and other cooling and heating devices. COP equals heat delivered as output, shown in British thermal units (BTUs), per hour divided by the heat equivalent of the electric energy input. The latter is calculated to be one watt = 3.413 Btu/hour, or, alternatively, energy efficiency ratio divided by 3.413. The higher the COP, the higher the efficiency of the equipment.
