AC efficiency calculator (EER, COP)
Compare air conditioners before buying by working out their real efficiency from two numbers on the energy label.
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How to use it
- Enter cooling capacity and electrical power input.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
EER = cooling capacity (BTU/h) ÷ electrical input (W). COP = EER × 0.293071. kW per ton = 12 ÷ EER.
Example
Inputs: Cooling capacity = 18,000 BTU/h, Electrical power input = 1,500 W. Result: Energy efficiency ratio (EER): 12 BTU/h per W; Coefficient of performance (COP): 3.52; kW per ton: 1 kW/TR.
Limits and caveats
- EER is measured at fixed test conditions; real performance drops in extreme heat.
- This is not a seasonal rating (SEER), which depends on part-load operation across a season.
Questions about this tool
What is the difference between EER and COP?
Both compare cooling to electricity. EER uses BTU/h over watts, while COP uses watts over watts and has no unit.
Is a higher number better?
Yes. A higher EER or COP means less electricity for the same cooling.
Where do I find the power input?
It is on the energy label or rating plate as the cooling power input in watts.