Refrigeration COP Calculator
Calculate the Coefficient of Performance (COP) of a refrigeration or air-conditioning system from its cooling load and compressor work. Use it to compare refrigeration system efficiency or verify measured operating data.
About this calculator
The Coefficient of Performance for a refrigerator (COP_R) measures how much cooling effect is delivered per unit of work input: COP_R = Q_L / W_comp, where Q_L is the cooling load (heat removed from the cold space, in W or kW) and W_comp is the compressor work input (W or kW). A COP of 3, for instance, means 3 J of heat is removed for every 1 J of electrical energy consumed. The theoretical maximum COP is set by the Carnot refrigeration cycle: COP_Carnot = T_cold / (T_hot − T_cold), with temperatures in Kelvin. Real vapour-compression systems typically achieve COP values of 2–5 for air conditioning and 1–3 for low-temperature refrigeration. Higher evaporator temperatures and lower condenser temperatures both improve COP.
How to use
A commercial refrigerator has an evaporator at −10 °C and a condenser at 40 °C. The cooling load (heat absorbed in the evaporator) is 3000 W and the compressor draws 1200 W. Apply the formula: COP = Q_L / W_comp = 3000 / 1200 = 2.5. This means the system delivers 2.5 W of cooling for every 1 W of electrical input. For comparison, the Carnot COP between these temperatures is T_cold / (T_hot − T_cold) = 263.15 / (313.15 − 263.15) = 263.15 / 50 = 5.26, so the real system operates at 2.5 / 5.26 ≈ 47.5% of the theoretical maximum.
Frequently asked questions
What is a good COP value for a refrigeration or air conditioning system?
For residential and commercial air conditioners (cooling mode), a COP between 3 and 5 is considered good; this corresponds to an Energy Efficiency Ratio (EER) of roughly 10–17 BTU/W·h. For low-temperature industrial refrigeration (below −20 °C), COP values of 1–2 are typical because the large temperature lift demands more compressor work. Ground-source heat pumps in cooling mode can achieve COP above 5. Always compare measured COP to the Carnot COP for the same operating temperatures to understand how close the system is to its thermodynamic limit.
How does evaporator temperature affect refrigeration COP?
Raising the evaporator temperature — while keeping the condenser temperature fixed — reduces the temperature lift that the compressor must overcome, directly improving COP. This is why supermarket display cases that operate at −5 °C are far more efficient than blast freezers at −35 °C. The relationship is captured by the Carnot COP formula: COP_Carnot = T_evap / (T_cond − T_evap). A 5 °C rise in evaporator temperature can improve real-system COP by 10–20%. Maintaining clean evaporator coils and adequate airflow keeps evaporating pressure high and COP near its design value.
What is the difference between COP of a refrigerator and COP of a heat pump?
Both devices use the same vapour-compression cycle, but they are valued for different outputs. A refrigerator's COP is defined as cooling load divided by compressor work (COP_R = Q_L / W), because the useful effect is the heat removed from the cold space. A heat pump's COP is defined as heat delivered to the warm space divided by compressor work (COP_HP = Q_H / W). Because Q_H = Q_L + W by energy conservation, COP_HP is always exactly 1 greater than COP_R for the same operating conditions. A system with COP_R = 3 therefore has COP_HP = 4 when run as a heat pump.