COP, EER, SEER Converter and Comparison Calculator

What do COP, EER and SEER tell you?

An air conditioner or heat pump moves more heat than the electricity it draws. Its efficiency is the ratio of the cooling or heating it delivers to the electrical power it takes.

• COP (coefficient of performance): capacity (W) over power input (W). It has no unit. A unit with a COP of 3.5 moves 3.5 kW of heat with 1 kW of electricity.
• EER (energy efficiency ratio): the same ratio in cooling. On European labels it is in W/W and equals the COP. US sources give it in BTU/Wh.
• SEER and SCOP: seasonal averages. Total energy delivered over a season divided by total electricity used, part load operation included.

Conversion relations

Since 1 watt is 3.412 BTU/h, EER (BTU/Wh) = 3.412 × COP. For chillers, kW/ton = 3.517 / COP = 12 / EER. Example: a COP of 3.5 gives an EER of 11.94 BTU/Wh and 1.005 kW/ton.

Comparing two units

Annual electricity use is the annual cooling demand divided by SEER. Of two air conditioners delivering 3000 kWh of cooling a year, the one with SEER 5.1 uses 588 kWh and the one with SEER 8.5 uses 353 kWh. The 235 kWh difference times your price per kWh is the annual saving.

If you do not know the annual cooling demand, a rough figure is capacity times equivalent full load hours per year. That number of hours varies widely with climate and use.

Points to watch

Label values are measured under standard test conditions. European and US SEER use different temperature profiles, so a unit conversion does not equate them: compare values rated to the same standard. Real consumption departs from the label with outdoor temperature, set point, installation quality and filter cleanliness.