Power Usage Effectiveness (PUE) is a metric created by The Green Grid to determine the energy efficiency of a data center. PUE is a ratio, with overall efficiency improving as the quotient decreases toward unity. In other words, PUE measures the extra power needed to power, cool, protect, and manage the IT load in a data center.
Since the issuance of PUE, many data center managers are under pressure to drive the PUE of their facility lower. The notion of driving energy efficiency is a noble one, but the drive toward a PUE target is not a pragmatic endeavor.
PUE should be viewed as a tool, not a destination. While the PUE is based upon very simple math, PUE comparisons are very difficult. In fact, it’s dangerous to compare PUE values between data centers because so much depends upon where (with respect to the facility infrastructure) PUE readings are taken, as well as which data center energy components are included in the scoring. There are simply too many variations from facility to facility and from operator to operator to know if one has a true “apples to apples” comparison.