Table of Contents
What Is COP?
The Coefficient of Performance (COP) is the ratio of useful heating or cooling provided to the work required. Unlike thermal efficiency (always less than 1), COP can be much greater than 1 because heat pumps and refrigerators move thermal energy rather than create it. A COP of 3 means the system provides 3 kW of heating for every 1 kW of electrical input.
COP is the primary metric for evaluating the efficiency of heat pumps, air conditioners, refrigerators, and chillers. The maximum possible COP is determined by the Carnot cycle and depends only on the temperature difference between hot and cold reservoirs. Real systems achieve 30-60% of the Carnot COP due to irreversibilities.
Formulas
Typical COP Values
| System | COP Range |
|---|---|
| Window AC | 2.5-3.5 |
| Air-source heat pump | 2.5-4.5 |
| Ground-source heat pump | 3.5-5.5 |
| Industrial chiller | 4-7 |
| Electric resistance heater | 1.0 (by definition) |
Frequently Asked Questions
Can COP be greater than 1?
Yes, and it normally is for heat pumps and refrigerators. COP > 1 does not violate thermodynamics because the device moves heat, not creates it. The work input drives heat from a cold reservoir to a hot one. Only the Carnot COP sets the theoretical maximum.
How does COP relate to SEER and EER?
EER (Energy Efficiency Ratio) is COP multiplied by 3.412 (to convert from W to BTU/h). SEER is the seasonal average EER accounting for varying outdoor temperatures. A SEER of 16 corresponds to an average COP of about 4.7.