PUE

PUE is the ratio of total facility power to the power that reaches IT equipment, and it expresses how efficient a datacenter is.

PUE is the ratio of the total power that a facility draws to the power that reaches IT equipment. The ratio expresses how efficiently a datacenter delivers power to the equipment that it hosts. A PUE of 1.1 is excellent, and at that value the facility draws 1.1 watts for every watt that reaches IT equipment. A PUE of 1.5 or more is common in older sites.