Coefficient of Performance Calculator

Coefficient of performance measures how effectively a heating or cooling system moves thermal energy compared with the energy it consumes. It is calculated as useful thermal output divided by work or electrical energy input. For a heat pump in heating mode, useful output is heat delivered indoors. For a refrigerator or air conditioner, useful output is heat removed from the cooled space. Because these devices move heat rather than converting all input energy directly into heat, COP can legitimately be greater than one. The equation is COP = useful energy output ÷ energy input. Both quantities must cover the same time period and use the same energy unit. Kilowatt-hours, British thermal units, and joules all produce the same dimensionless ratio when used consistently. A heat pump that delivers 12.6 kWh of heat while consuming 3.5 kWh of electricity has a COP of 3.6. That means it moves 3.6 units of useful heat for every unit of purchased energy. COP depends strongly on operating conditions. A heat pump generally performs better when the temperature difference between its source and destination is small. Cold outdoor air, high supply-water temperatures, frost, dirty coils, poor airflow, compressor cycling, and auxiliary resistance heat can reduce real performance. Refrigeration COP likewise varies with evaporating and condensing temperatures, equipment loading, and maintenance. A manufacturer's rated value applies only at specified test conditions. The percentage shown by this calculator is simply COP multiplied by 100 and is best described as an output-to-input ratio, not conventional conversion efficiency. Calling a COP of 3.6 a 360 percent efficiency can be misleading because energy is conserved: the additional heat comes from the surrounding environment. For meaningful comparisons, use measured energy totals over matching boundaries and time intervals. Do not mix cooling capacity in kilowatts with electrical consumption in kilowatt-hours without accounting for operating time. Seasonal metrics such as SCOP, HSPF, SEER, or measured annual COP are often more representative than a single operating-point result.