Definition: PUE

(Power Usage Effectiveness) In a datacenter, the ratio of electrical power used by the servers in contrast to the total power delivered to the facility. Used to measure the effectiveness of cooling systems, the perfect PUE would be 1, which means that all the power coming into the room is used by the servers inside. In practice, 1.6 would be extremely efficient, because the average datacenter PUE is 2.5.