PUE is a measure of efficiency mostly used in data centres. This and reliability are two key parameters for these installations. PUE reports are used to maximise the efficiency of a data centre. PUE is –

Power from grid / Power to server racks

A perfect system would have a PUE of 1 and the majority of losses are due to cooling for the servers and other support tasks.

The 3 circuits in sub.net can be used to calculate PUE. For larger installations other sub.nets or transducers monitoring all the loads can be connected together to record and report the PUE value and trend.