EER to COP Calculator

Last updated: 2026-08-24

EER to COP Calculator — Convert Energy Efficiency Ratio (EER) to Coefficient of Performance (COP) using the standard conversion factor.

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How to Use This Calculator

This EER to COP calculator is designed to help you quickly and accurately convert the Energy Efficiency Ratio (EER) of an HVAC system into its equivalent Coefficient of Performance (COP). To use the calculator, simply enter the EER value (in BTU per watt-hour) into the input field and click the calculate button. The COP value will be displayed instantly. This tool is especially useful for engineers, technicians, and homeowners who need to compare efficiency ratings across different systems or standards. For example, if you have an air conditioner with an EER of 12.0, the calculator will show you that its COP is approximately 3.52. This conversion helps bridge the gap between US and international efficiency metrics.

Formula and Methodology

The conversion from EER to COP is based on the fundamental relationship between British Thermal Units (BTU) and watt-hours. One BTU is equal to 0.293071 watt-hours. Therefore, to convert EER (BTU/Wh) to COP (W/W), you multiply the EER by 0.293. Mathematically, the formula is: COP = EER × 0.293. This simplified factor (0.293) is accurate enough for most practical purposes. The exact factor is 0.293071, but using 0.293 gives results within 0.02% accuracy. This conversion is widely used in the HVAC industry when comparing equipment rated with different efficiency metrics. It is important to note that EER is measured at a specific set of operating conditions (typically 95°F outdoor, 80°F indoor), while COP can vary significantly with operating conditions. Always verify the test conditions when comparing values.

Practical Examples

Example 1: A window air conditioner has an EER of 10.5. What is its COP? Using the formula: COP = 10.5 × 0.293 = 3.0765. Rounded to two decimal places, the COP is 3.08. This means the air conditioner produces 3.08 units of cooling for every 1 unit of electricity consumed.

Example 2: A central air conditioning system is rated with an EER of 13.2. Calculate the COP. COP = 13.2 × 0.293 = 3.8676. Rounded, we get 3.87. This higher COP indicates a more efficient system.

Example 3: A commercial chiller has an EER of 16.8. The COP would be: 16.8 × 0.293 = 4.9224, or about 4.92. Such high COP values are typically seen in large, high-efficiency systems.

Tips and Best Practices

When using EER to COP conversion, always ensure you have the correct EER value — some ratings may be SEER (Seasonal Energy Efficiency Ratio) which is an average over a cooling season, not a single-point measurement. For accurate conversion, use the EER value from the manufacturer’s spec sheet under standard conditions. Also, remember that COP values above 4.0 are generally excellent, but they can be higher for geothermal heat pumps. If you are comparing systems, use the same conversion method for all units to maintain consistency. For precise engineering calculations, consider using the exact factor 0.293071, though the difference is negligible for most applications. Finally, note that this conversion does not account for fan power or other system losses — it is a direct conversion of the rated efficiency numbers.

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FAQ

What is the difference between EER and COP?

EER (Energy Efficiency Ratio) is a measure of how efficiently an air conditioner or heat pump operates, expressed in BTU per watt-hour. COP (Coefficient of Performance) is a dimensionless ratio of heating or cooling output to electrical input. Both measure efficiency, but they use different units. EER is more common in the US, while COP is used internationally.

Why do we multiply EER by 0.293 to get COP?

The conversion factor 0.293 comes from the relationship between BTU and watts: 1 BTU = 0.293071 watt-hours. Since EER is in BTU/Wh and COP is dimensionless (W/W), dividing EER by 3.412 (or multiplying by 0.293) gives the equivalent COP. So COP = EER × 0.293.

Can this calculator be used for both heating and cooling?

Yes, this conversion works for both heating and cooling efficiency ratings. However, note that for heat pumps, you may also encounter HSPF (Heating Seasonal Performance Factor) which uses a different conversion. For cooling, EER and SEER can both be converted to COP using the same factor.

What is a good COP value for an air conditioner?

Typical COP values for modern air conditioners range from 2.5 to 4.0. A COP above 3.0 is considered good, above 3.5 is excellent. For comparison, an EER of 10 corresponds to a COP of about 2.93, and an EER of 14 gives a COP of about 4.1.