Power usage effectiveness (PUE) is a ratio that describes how efficiently a computer data center uses energy; specifically, how much energy is used by the computing equipment (in contrast to cooling and other overhead).
PUE is the ratio of total amount of energy used by a computer data center facility to the energy delivered to computing equipment. PUE is the inverse of data center infrastructure efficiency (DCIE).
PUE was originally developed by a consortium called The Green Grid. PUE was published in 2016 as a global standard under ISO/IEC 30134-2:2016
An ideal PUE is 1.0. Anything that isn’t considered a computing device in a data center (i.e. lighting, cooling, etc.) falls into the category of facility energy consumption