General information about refrigeration
11. April 2017

EER - Energy Efficiency Ratio of refrigeration systems

EER - Energy Efficiency Ratio of refrigeration systems

The EER Energy Efficiency Ratio

describes the relationship between power consumption and discharged cooling capacity. It is determined under the following measuring conditions: 35 °C outside air temperature / 27 °C inside air temperature. Thus, the EER is determined analogously to the COP value.



EER Energy Efficiency Ratio 
QK Cooling capacity 
PEL electrical power consumption

That means at a value of 3,1 kilowatt of electric power is required to generate 3 kilowatts of cooling capacity.


What does a difference of 0.6 mean?

Comparison of 2 hypothetical chillers

  1. Cooling capacity: 350 KW
  2. Outside air temperature: 35 °C
  3. Water inlet / outlet: 12/7 °C
  4. Operating hours / a 4000 h
  5. Energy price: 0.18 €/kWh


Cost analysis EER


Der ESEER ( European Seasonal Energy Efficiency Ratio)

was introduced to describe the energy efficiency of a chiller throughout the year. This means that the calculation does not take place as in the EER exclusively in full load operation, but also includes the partial load conditions. The following weighting is used:



Multinational experiences of professionals have been used to create this distribution. The ESSER is calculated as follows:

ESEER = (EER at 100% x 0.03) + (EER at 75% x 0.33) + (EER at 50% x 0.41) + (EER at 25% x 0.23)

As a result, the load conditions characteristic of the year can be assessed.




For industrial applications almost only full load conditions are relevant. Since these are only slightly weighted in the calculation of the ESEER, it makes sense to follow the EER.

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