Heat pump guide
Heat Pump COP and Operating Cost
Use a known load, a matching COP, and a local electricity rate to evaluate one operating scenario without treating a point estimate as a seasonal bill forecast.
Start with the operating condition
Coefficient of performance (COP) is useful only when its output and input apply to the same condition. For heating, it is useful heat delivered divided by electrical energy consumed. For cooling, it is useful cooling delivered divided by electrical energy consumed. A COP of 3 means the stated condition delivers three units of useful thermal energy for each unit of electrical input.
Cost calculation method
Operating cost = electrical energy (kWh) × electricity rate (currency/kWh)
When the load is in BTU/h, multiply by operating hours and divide by 3,412.141633 to obtain kWh thermal. When the load is in kW thermal, multiply directly by hours. This separates thermal output from electrical input.
Worked heating example
Suppose the documented heating load is 24,000 BTU/h for 8 hours. Useful heat is 192,000 BTU, or 56.30 kWh thermal. At COP 3, the heat pump uses 18.77 kWh. With an electricity rate of 0.15 currency/kWh, the scenario costs 2.82 currency. An electric-resistance heater delivering the same heat at COP 1 would use 56.30 kWh and cost 8.45 currency.
What to collect before calculating
| Item | Why it matters | Where to find it |
|---|---|---|
| Useful load | Operating cost follows the heat or cooling actually required. | A documented load calculation, monitored system data, or a defined scenario. |
| Point COP | It converts useful output to electrical input. | Manufacturer performance data or controlled measurement at matching conditions. |
| Runtime | Converts a rate to energy. | A defined operating schedule or measured interval. |
| Marginal electricity rate | Prices the consumed kWh. | Your utility tariff; account separately for demand, fixed, or time-of-use charges. |
Do not mix point and seasonal ratings
SEER2 and HSPF2 are seasonal efficiency ratings obtained under prescribed test procedures. They are valuable for comparing certified equipment but are not the same as an instantaneous COP at a particular outdoor temperature, load, or defrost state. Use an equipment's matched-condition COP in a short scenario calculation, or use a whole-season method that explicitly uses seasonal data and a local load profile.
Practical interpretation
Cost changes with both load and COP. A lower building load reduces energy use, while a lower COP increases the electricity required per unit of useful heat or cooling. The calculation therefore supports a narrow question: “What does this known operating scenario cost?” It cannot confirm equipment capacity at design temperature, predict an annual utility bill, or specify a backup-heat changeover point.
Related tools and reference
- Heat Pump Operating Cost Calculator
- Heat Pump Efficiency Ratings Reference
- HVAC Load Calculator
- BTU/h vs kW
Sources and scope
This guide uses the official definitions of COP and seasonal metrics and a NIST unit conversion. It does not prescribe ratings, equipment selection, or operating temperatures.