Power Usage Effectiveness (PUE) is a standard developed to measure energy efficiency within a data center. PUE was developed by a consortium called The Green Grid. One can calculate the PUE of a data center simply by dividing the amount of energy required to power the data center by the amount of energy actually used by the IT equipment. In this context IT equipment comprises servers, storage (disk arrays, SAN, NAS), telecom equipment (routers, switches) and any piece of equipment that provides an IT service.
PUE = Total facility power / IT Equipment power
Total facility power could also be written as Cooling + Power +Lighting + IT
One view of PUE is that it is the “tax” or burden in energy costs you must pay above the IT load to run the data center. A PUE = 1.0 means 100% of the energy you bring in to the data center goes to the IT.(1)
The following charts illustrate the distribution of electricity across major components of a data center.