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How to Use the COP Calculator
Choose the system type, then enter the heat transfer rate in BTU/hr and the electrical power input in watts. Include fan power in the watts if you want a whole-system COP. The result is the COP at the conditions you measured.
Optionally enter the low and high saturation temperatures in °F, taken from pressures with the P-T chart calculator. The calculator then shows the Carnot COP for that lift and the percentage of it your system achieves.
Switch to Convert mode, pick EER, EER2, SEER, SEER2, HSPF or HSPF2, and enter the nameplate value. The calculator divides by 3.412 and shows the COP, noting that seasonal ratings are averages.
For SEER2, HSPF2 and EER2 ratings, the results list the 2026 Canadian minimums and ENERGY STAR levels in the same units and in COP, and say whether your rating meets each one.
COP and what it means for Canadian HVAC efficiency
COP, the coefficient of performance, is the useful heating or cooling a system delivers for each unit of electrical energy it uses. A COP of 3.0 means three units of heat moved per unit of electricity. An electric resistance heater is exactly 1.0, so any heat pump above that is delivering more heat than the electricity it consumes, which is why heat pumps feature so heavily in Canadian decarbonisation plans.
COP, EER, SEER2 and HSPF2
EER is COP multiplied by 3.412, expressed in BTU/hr per watt at a single test condition. SEER2 averages cooling efficiency across a season, and HSPF2 does the same for the heating season, both using the revised test procedure with higher external static pressure. Dividing any of them by 3.412 gives an equivalent COP: EER 12 is 3.52, and SEER2 13.4 is 3.93. The SEER to COP converter handles the seasonal conversion on its own.
Because the test is tougher, SEER2 and HSPF2 numbers run lower than SEER and HSPF for the same equipment, typically by roughly 10-15%, with no single fixed ratio. Seasonal ratings are averages, so they will not match a COP measured at one set of conditions.
Canadian minimums and ENERGY STAR
Amendment 18 to the Energy Efficiency Regulations, 2016, published in Canada Gazette, Part II on April 9, 2025, sets SEER2 and HSPF2 minimums for units made on or after January 1, 2026. A split air conditioner needs SEER2 13.4 (COP 3.93). A split heat pump needs SEER2 14.3 (COP 4.19) and an HSPF2 of 6.0 for Region V (COP 1.76). The earlier split heat pump levels, SEER 14.0 and HSPF 7.1, were in the older metrics and should not be read as HSPF2 values.
ENERGY STAR key criteria for split air-source heat pumps are SEER2 15.2 (COP 4.45), HSPF2 7.8 (COP 2.29) and EER2 11.0 (COP 3.22). Those criteria are published by the U.S. program, so check the Canadian ENERGY STAR listing for the units you are specifying. Seasonal COP from a rating is approximate, because the ratings include defrost and backup heat effects.
Measuring actual COP in the field
A field COP needs two numbers: heat transfer and electrical input. Capacity comes from equipment data or a heat meter, and power should be measured in watts. A clamp meter reading in amps overstates power on an inductive load, so multiply by voltage and power factor, which the power factor calculator covers. The example, 24,000 BTU/hr on 2,200 W, is a COP of 3.20 and an EER of 10.9.
If the answer is above 10, the units are almost certainly wrong, usually kW against W or MBH against BTU/hr, and the calculator stops with a message rather than reporting it.
Why COP falls in cold weather
COP is not one number, because the compressor works harder as the temperature lift grows. For a heat pump the lift is largest on the coldest days. The ENERGY STAR air-source heat pump criteria define cold-climate units by a COP of at least 1.75 at 5°F (-15°C) and heating capacity at 5°F of at least 70% of the 47°F capacity. Even 1.75 delivers 75% more heat than resistance, but it is far from the mild-weather figure.
Carnot COP and percent of Carnot
Carnot COP is the theoretical maximum between two absolute temperatures: low over (high minus low) for cooling, and high over (high minus low) for heating. For 40°F and 110°F, cooling gives 500 / 70, which is 7.14. A measured COP of 3.20 is 45% of that. A saturated ideal vapour compression cycle reaches about 78-81% of Carnot for R-134a, R-22 and R-32 between those temperatures, and about 63% for R-404A at -10°F and 100°F, per real-fluid property data. Compressor, motor and fan losses account for the rest.
Frequently Asked Questions
There is no single number, because COP falls as the outdoor temperature drops. A useful benchmark is the ENERGY STAR cold-climate requirement of a COP of at least 1.75 at 5°F (-15°C), with heating capacity at that temperature of at least 70% of the 47°F capacity. For seasonal ratings, the Canadian minimum for a split heat pump built from 2026 is an HSPF2 of 6.0 (Region V), a COP of about 1.76, while the ENERGY STAR level of 7.8 corresponds to about 2.29. Compare a measured COP with the manufacturer's table at the same outdoor and indoor temperatures. If it is well below that table, check charge with the superheat calculator and airflow across both coils.
Divide EER by 3.412. EER is in BTU/hr per watt, and 3.412 BTU/hr equals one watt, so the result is the dimensionless COP. An EER of 12 is a COP of 3.52. SEER and SEER2 convert the same way but give a seasonal average, so SEER 16 is about 4.69 and SEER2 13.4 is about 3.93. Going the other way, multiply COP by 3.412. The Convert mode above does this for EER, EER2, SEER, SEER2, HSPF and HSPF2.
Carnot COP is the ceiling for any cycle working between two temperatures, so the percentage of Carnot puts systems with different temperature lifts on one scale. In the example, 40°F evaporating and 110°F condensing give a Carnot COP of 7.14, and a measured COP of 3.20 is 45% of it. A saturated ideal vapour compression cycle on R-134a, R-22 or R-32 reaches about 78-81% of Carnot between those temperatures, and R-404A at -10°F and 100°F reaches about 63%. Compressor, motor and fan losses take the rest, so reading 100% is impossible and a falling percentage over time is the useful signal.
The older HSPF and SEER tests used light external static pressure, which flattered ducted equipment compared with real installations. HSPF2 and SEER2 use a revised procedure with higher static pressure, so the same unit scores lower, typically by roughly 10-15%, and there is no single fixed ratio. In Canada, Amendment 18 to the Energy Efficiency Regulations, 2016 applies SEER2 and HSPF2 minimums to units made on or after January 1, 2026, replacing the earlier SEER 14.0 and HSPF 7.1 split heat pump levels. Do not compare an old HSPF figure directly with a new HSPF2 figure, because the older number looks better for the same equipment.