Refrigeration COP Calculator

Coefficient of performance (COP) measures a refrigeration system's efficiency as the ratio of heat removed from the cold space to the work input required, unlike heat engine efficiency, COP can be greater than 1, since a refrigerator moves more heat energy than the work energy it consumes.

COP_R = Tc/(Th−Tc), where Th and Tc are the absolute (Kelvin) temperatures of the hot (heat rejection) and cold (refrigerated space) reservoirs. This is the Carnot (reversible) COP, the theoretical maximum for any refrigerator operating between those two temperatures.

A refrigerator doesn't create the heat it moves, it uses work input to pump existing heat from a cold space to a warmer surroundings, so the heat removed can exceed the work input, giving a COP greater than 1, often considerably so for small temperature differences.

EER (Energy Efficiency Ratio), common on US air conditioner labels, expresses cooling capacity in BTU/h per watt of power input. EER = COP × 3.412 (the conversion factor between watts and BTU/h), this calculator reports both values.

Since COP=Tc/(Th−Tc), a smaller gap between Th and Tc makes the denominator smaller relative to Tc, increasing COP. This is why home refrigerators (small internal-to-room temperature gap) have much higher COPs than deep freezers or systems cooling to very low temperatures.

No, like the Carnot heat engine, the Carnot refrigeration cycle assumes perfectly reversible operation with no friction or irreversible heat transfer, conditions no real system achieves. Real refrigerators and air conditioners achieve a fraction of this theoretical maximum.

Modern household refrigerators typically have real-world COPs in the range of 2-4, well below their theoretical Carnot maximum (which can be considerably higher for the small temperature difference involved), reflecting real compressor and heat-exchanger inefficiencies.

A heat pump uses the exact same refrigeration cycle but focuses on the heat delivered to the hot side rather than the heat removed from the cold side, giving COP_HP = COP_R + 1, always exactly 1 higher than the refrigeration COP for the same two temperatures.

A wider gap between the cold space and the surroundings (like a deep freezer at -18°C rejecting heat to a 25°C room) forces the compressor to do proportionally more work per unit of heat removed, directly lowering COP, this is why freezers use noticeably more energy per unit of cooling than refrigerators.

Both reservoir temperatures must be entered in Kelvin (absolute temperature). COP itself is dimensionless, EER is reported in BTU/(h·W).