Understanding Heat Pump COP
COP means coefficient of performance. It compares useful heating delivered with energy supplied. A heat pump can move heat instead of making all heat directly. That is why COP can be higher than one. A COP of three means three kilowatt hours of heat are delivered for each kilowatt hour used.
Why COP Changes
COP is not fixed. It changes with source temperature, sink temperature, airflow, refrigerant charge, defrost cycles, and auxiliary heat. A small temperature lift usually gives better performance. A large lift makes the compressor work harder. Cold outdoor air can reduce output and raise running cost.
Measured And Ideal Performance
This calculator separates measured COP from Carnot COP. Measured COP uses real heat output and electrical input. Carnot COP is an ideal upper limit based on absolute temperatures. Real systems always stay below that limit. The ratio between measured COP and Carnot COP helps show how efficiently the machine uses the available thermodynamic limit.
Energy And Cost View
Power values describe the instant operating point. Hours and electricity price convert that point into daily and monthly estimates. Defrost loss and auxiliary heat settings give a more practical result. These options are useful when comparing field measurements with brochure data, design targets, or utility bills.
Using The Results
Use the COP result as a performance indicator, not a complete system audit. Check that heat output and electric input were measured over the same period. Make sure units are correct. When temperatures are used, choose the hot side and cold side temperatures near the heat exchangers. Review the energy balance if absorbed heat is entered. A large residual can reveal a wrong unit, sensor error, or mixed test condition.
Practical Notes
High COP usually means lower operating cost. Yet comfort and capacity still matter. A small heat pump with high COP may not heat the space during peak load. A larger unit may cycle often in mild weather. Compare COP with load, climate, controls, and installation quality. Good airflow, clean coils, correct charge, and proper ductwork can improve real performance.
Record outdoor temperature with each test. Recheck results after filter changes, service work, or weather shifts. Consistent records make future performance checks easier and clearer.