Power Usage Effectiveness (PUE) is a metric used to determine the energy efficiency of a data center. It is calculated by dividing the total amount of energy used by the data center by the energy used by the IT equipment. The formula is: PUE=Total Facility Energy/IT Equipment Energy - **Purpose**: PUE helps data centers optimize their energy consumption by identifying the efficiency of their power usage. A lower PUE indicates higher efficiency, as more of the energy is used by the IT equipment rather than overhead (e.g., cooling, power distribution). - **Benchmark**: An ideal PUE is 1.0, meaning all the energy is used by the IT equipment. Realistically, a PUE of 1.2 to 1.4 is considered very efficient [[2](https://www.digitalrealty.co.uk/resources/articles/what-is-power-usage-effectiveness), [3](https://www.techtarget.com/searchdatacenter/definition/power-usage-effectiveness-PUE)].