How to use the cooling efficiency converter
- Choose to convert an efficiency rating or a cooling capacity.
- For a rating, pick EER, COP or kW per ton and enter the value.
- For a capacity, pick tons, Btu per hour, MBH, kilowatts or kilocalories per hour and enter the value.
- Read the other units, and copy or print the result for a spec sheet.
Formula
COP = EER / 3.412141633 (1 watt hour = 3.412141633 Btu)
kW per ton = 12 / EER, because 1 ton = 12,000 Btu/h
EER = 12 / (kW per ton) = COP x 3.412141633
1 ton = 12,000 Btu/h = 3.51685 kW; 1 Btu/h = 0.29307107 W; 1 kcal/h = 1.163 W
EER is the cooling output in Btu per hour for each watt of electricity, and COP is the same ratio with both in watts. They differ only by the unit of the cooling output.
Three common conversions
An EER of 12 is a COP of 3.51685 and uses 1 kW per ton. A COP of 3.5 is an EER of 11.9425. A chiller at 0.8 kW per ton has an EER of 15 and a COP of 4.39607.
A capacity of 3 tons is 36,000 Btu/h, 36 MBH, 10.55056 kW and 9,071.847 kilocalories per hour.
Reading the ratings
A higher EER or COP, or a lower kW per ton, means less electricity for the same cooling. Window units and small air conditioners are often labeled with EER, heat pumps and chillers with COP, and large chillers with kW per ton. Seasonal ratings are measured differently, so a seasonal number is the same kind of ratio but not the same test.
To size the airflow for a cooling load use the HVAC airflow heat calculator, and to put the electric power in context see the electricity cost calculator.
What a ton means
A ton of cooling is a rate of heat removal, not a weight. It comes from the heat needed to melt a ton of ice in a day, and it is fixed at 12,000 Btu per hour. MBH means thousands of Btu per hour and is common on equipment labels.
Assumptions and limits
- A ton is the ton of refrigeration, fixed at 12,000 Btu per hour (3.51685 kW).
- The Btu is the International Table Btu, with 1 Btu/h equal to 0.29307107 W.
- Ratings measured at different conditions are converted as plain ratios. The conversion does not adjust for the test.
- Displayed values are rounded to 6 or 7 significant digits.
Frequently asked questions
How do I convert EER to COP?
Divide the EER by 3.412141633. An EER of 12 is a COP of about 3.517.
How do I convert kW per ton to EER?
Divide 12 by the kW per ton. A chiller at 0.8 kW per ton has an EER of 15.
How many kilowatts is one ton of cooling?
One ton is 12,000 Btu/h, which is 3.51685 kW of heat removal.
Is a higher COP better?
Yes. A higher COP or EER means more cooling for each watt of electricity, while a lower kW per ton means the same.