Power usage effectiveness (PUE) is a measure of how efficiently a computer data center uses its power; specifically, how much of the power is actually used by the computing equipment (in contrast to cooling and other overhead).
PUE= Total facility power /IT equipment power
PUE is the ratio of total amount of power used by a computer data center facility to the power delivered to computing equipment.
PUE is the inverse of data center infrastructure efficiency (DCiE). An ideal PUE is 1.0.