Efficiency
COP
A dimensionless ratio comparing useful heating or cooling delivered with the work supplied to the system.
What is COP?
COP stands for Coefficient of Performance. For a heat pump, it compares the useful heating or cooling effect with the net work input when both are expressed in the same energy units. A heating COP of 3 means the system is delivering three units of heat to the conditioned space for each one unit of work input under the stated test or operating condition.
COP is dimensionless because the output and input are expressed in equivalent units before the ratio is calculated. Unlike a seasonal rating such as HSPF2, COP is usually associated with a particular operating or rating condition.
Heat-pump COP can change as outdoor temperature, indoor temperature, compressor speed, and other operating conditions change. A single COP value should therefore be read together with the condition at which it was measured.
Why it matters
COP is especially useful for understanding why heat pumps can deliver more heat energy to a building than the electrical work they consume: they move heat rather than converting electricity directly into heat at a one-to-one ratio.
Formula / Conversion
COP = useful heating or cooling effect ÷ net work input
Sources
HVACBird prioritizes government standards bodies, federal test procedures, and recognized HVAC certification organizations for technical definitions.
U.S. Department of Energy
DOE definition of coefficient of performance for air conditioners and heat pumps.
Related HVAC Terms
Heat Pump
Heating and cooling equipment that uses a refrigeration cycle to move heat between locations.
HSPF2
A seasonal heating-efficiency rating for air-source heat pumps.
SEER2
A seasonal cooling-efficiency rating used for central air conditioners and heat pumps.
EER2
A cooling-efficiency rating measured at a specified full-load test condition.