A. Power Usage Effectiveness (PUE)
The PUE metric was developed by Green Grid. It has been widely adopted by industry according to the Green Grid. ENERGY STAR has also adopted the PUE calculation. PUE measures the ratio of data center facility energy use to the energy in the ICT services delivered to end consumers, where facility energy includes everything that supports the ICT equipment, like lighting, heating, cooling, and the ICT equipment energy is the servers, computers, network equipment. A 100% efficient data center would have a PUE of 1.0, where every kWh of supporting energy serves a kWh of ICT equipment energy. According to a GreenGrid/EPA joint presentation, a 2.0 PUE is typical in the industry; 1.2 PUE is best in class.
B. Energy intensity metric (bits per kWh)
Another metric developed by the Green Grid is the bits per kWh consumed, a performance metric. This metric measures the output of a data center (in data unit ‘bits’) compared to the amount of energy used to deliver the bit to a customer. A bit is the basic unit of information in computing and digital communications.