CER - STULZ answers

Saving energy has been high on the agenda of data centres for many years, and largely determines the success of a data centre. Possibilities are constantly sought to reduce energy consumption on the data floor and its environs. For that reason, the Cooling Efficiency Ratio (CER) is used to assess the efficiency of a cooling system within a data centre. This indicator represents the ratio of total heat dissipated within a data centre to the power consumption of the cooling systems.

The metric only gives an indication of how efficient the cooling system is in a data centre and should be used as an internal KPI to measure improvements in energy consumption.

Calculating the Cooling Efficiency Ratio (CER)
The CER value reflects the ratio of the total amount of heat released from the data centre per year in kWh (Q) and the energy consumption (per year) of the cooling systems in kWh (E) over the same time period (T).

CER = Q_removed / E_cooling