Heat Pump COP Calculator
Calculate heat pump coefficient of performance and savings. Calculates actual COP, Carnot COP, and system efficiency. When operating hours and costs are…
Calculates actual COP, Carnot COP, and system efficiency. When operating hours and costs are provided, compares heat pump vs boiler operating costs to estimate annual savings.
What is Heat Pump COP?
The Coefficient of Performance (COP) measures heat pump efficiency — the ratio of heating output to electrical input. A COP of 4.0 means the system delivers 4 kW of heating for every 1 kW of electricity consumed, effectively providing 300% 'free' energy from the environment.
COP depends primarily on the temperature difference between heat source and sink. The theoretical maximum (Carnot COP) = T_sink / (T_sink - T_source) in Kelvin. Real heat pumps achieve 40-60% of Carnot COP. Air-source heat pumps typically have COP 2.5-4.5, ground-source 3.5-5.5.
Seasonal COP (SCOP) averages performance across the entire heating season, accounting for varying outdoor temperatures. SCOP is a better indicator of real-world performance than peak COP, as COP drops significantly in very cold weather when the temperature lift is largest.
Formula: COP = Heating Output (kW) / Electrical Input (kW) Carnot COP = T_sink(K) / (T_sink(K) - T_source(K)) Carnot Efficiency = Actual COP / Carnot COP
Example Calculation
Air-source heat pump: outdoor 5°C (278K), indoor 35°C (308K). Carnot COP = 308/(308-278) = 10.27. Real COP at 45% Carnot efficiency = 4.62. Heating 10 kW output → 2.16 kW electrical input. vs Gas boiler (90% eff): 10/0.9 × gas cost. If electricity $0.15/kWh vs gas $0.06/kWh: HP cost $0.324/hr vs boiler $0.667/hr — 51% savings.
When to Use This Calculator
- HVAC engineers comparing heat pump vs gas/oil boiler operating costs for new building design or retrofit projects
- Homeowners evaluating air-source or ground-source heat pump investments against current heating costs
- Energy consultants sizing heat pump systems by verifying COP at actual site conditions (outdoor design temperature)
- Building services designers checking whether a heat pump can meet heating demand at low outdoor temperatures or if auxiliary heating is needed
Common Mistakes to Avoid
- Using manufacturer peak COP (tested at mild conditions) instead of seasonal COP — SCOP accounts for varying outdoor temperatures and defrost cycles throughout the heating season
- Ignoring auxiliary/backup heating costs — at very low temperatures, COP drops below 2.0 and resistance heating may engage, dramatically increasing electricity consumption
- Comparing COP without considering electricity vs fuel price ratio — a COP of 3.0 is not cost-effective if electricity costs 4× more than gas per kWh
- Forgetting to include standby power, circulation pumps, and defrost energy in the total electrical input calculation
How to Interpret Results
- If COP is below 2.5 at design conditions, the heat pump may not be cost-effective vs a high-efficiency gas boiler — compare annual operating costs directly
- If Carnot efficiency is below 35%, the heat pump system may have performance issues (undersized heat exchangers, incorrect refrigerant charge)
- If annual savings are positive but payback exceeds 10 years, consider whether equipment lifetime (15-20 years) still makes the investment worthwhile vs alternative heating improvements
Related Standards & References
- EN 14511 — Air conditioners, liquid chilling packages and heat pumps — Testing and rating at standard conditions
- EN 14825 — Testing and rating at part load conditions and calculation of seasonal performance (SCOP)
- AHRI 210/240 — Performance Rating of Unitary Air-conditioning and Air-source Heat Pump Equipment
- ASHRAE Handbook — HVAC Systems and Equipment — COP and Carnot cycle analysis conventions for heat pumps
Frequently Asked Questions
At what temperature does a heat pump stop being efficient?
Most air-source heat pumps maintain COP > 2.0 down to -15°C and can operate to -25°C with newer inverter-driven compressors. Below COP 2.5-3.0, a heat pump may cost more to run than a gas boiler depending on electricity/gas price ratio. Ground-source heat pumps maintain higher COP year-round.
What is the difference between COP and EER?
COP measures heating efficiency, EER (Energy Efficiency Ratio) measures cooling efficiency. Both are output/input ratios, but EER is traditionally expressed in BTU/Wh while COP is dimensionless (kW/kW). SEER is the seasonal cooling equivalent of SCOP.