The Green Grid, an industry trade consortium focused on improving energy efficiency, developed the PUE metric. The metric compares the total amount of energy consumed by the data center with the total amount of energy consumed by the data center's IT equipment. A rating below 2 is highly effective; above 3, and there are bigger problems than the IT gear.
PUE = Total data center facility power consumption / IT equipment power consumption
Data Center infrastructure Efficiency (DCiE) is the reciprocal of PUE (1 / PUE), defined as:
DCiE = IT equipment power consumption / Total data center facility power consumption x 100%
Note that The Green Grid defines PUE as being greater than or equal to 1.0, and DciE as being greater than or equal to 100 percent.
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Overall, IT administrators should use the PUE metric along with other measurements to effectively manage their environments. After all, the most important metrics are the ones that provide situational awareness into how your environment is functioning to deliver information services at a given level.
The Green Grid defines four classes of reporting PUE, which are important for understanding if the results are more ad hoc or formalized and the context of them: