EER, SEER, and COP. No, Not Code Languages

Efficiency of air conditioning units are measured using EER, SEER, and COP.

These stands for,

Metaphor of energy saving by having higher efficiency air conditioner

  • energy efficiency ratio,

  • seasonal energy efficiency ratio, and

  • coefficient of performance, respectively

and explained in brief, on air conditioner buying guide page.

Efficiency in air conditioning cycle:

We have to bear in mind that the cooling effect that we get from air conditioning units come from a form of energy called electricity.

We also have to bear in mind that we won’t always get the amount of energy removal in terms of heat, per energy input from electricity.

Energy will be lost through,

  • undesired heat loss or gain,

  • noise, and

  • friction

Energy losses are inevitable, especially in mechanical and machinery systems, and air conditioners are not left out.

Enough jargon. Let’s get to the business.

General definition of efficiency is,

output divided by input

In detail for air conditioning,

Definition 1: EER, energy efficiency ratio:

Is the measure of air conditioner efficiency at maximum air conditioning load.

It is measured by ratio of Btu/hour of cooling or heating load, to watts of electrical power input.

The unit is in Btu hr-1 W-1.

Definition 2: SEER, seasonal energy efficiency ratio:

The measurement units of SEER is exactly the same as EER, but the difference lies in the data used for the measurement.

Values for SEER, is determined through averaging readings of different air conditions, to represent air conditioner efficiency throughout the season.

Definition 3: COP, coefficient of performance:

COP is defined as the cooling load, in kW, to power input at the compressor, in kW.

The definition is very close to EER, but the units are different.

Useful information about EER, SEER, and COP:

You have to keep these in mind, the next time you’re shopping around for air conditioners. These are,

  • value for EER is normally measured at 35 oC (95 oF) of outside dry bulb temperature, and 27 oC (80 oF) of inside dry bulb temperature

  • value for SEER is normally measured under averaged air conditions, at the manufacturers area.

    The value won’t be the same if you’re installing the unit at an area with different average air conditions.

    However, you can ask the conditions at which the air conditioners are tested at. Normally, air conditioners will be tested against same air conditions.

    Hence, it is accurate to select an air conditioner with higher SEER

  • it is also better to select air conditioners based on SEER, rather than EER.

    It will be useful in calculating the averaged and expected seasonal energy usage.

    You can still use EER.

    BUT, dot not compare two air conditioners, one based on SEER, and the other based on EER. The selection process will be flawed.

  • COP values are normally used to measure efficiency of an air conditioner or heat pump, during design stage. It is very rarely used by consumers

  • values for all three efficiency numbers are dependent on different criteria.

    Inside and outside air temperature difference, compressor’s efficiency, condenser’s efficiency, evaporator’s efficiency, expansion device’s efficiency, and fan’s efficiency.

    Example: Replacing an air conditioning unit with a lower efficiency compressor, will require the compressor to draw in more power, for the same cooling effect. Efficiency drop we have.

    These are not fixed numbers. Values will change over time as the air conditioner ages

  • maintaining the air conditioner at optimum condition will help in maintaining a high efficiency number

Oh yes, some useful conversion factors. NOTE that EER and COP conversion holds if these are measured at the same air conditions,

1depends on average test conditions, but normally 14% - 20% higher than EEREER X 0.293

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