Power Usage Effectiveness (PUE)

For a long time, Power Usage Effectiveness (PUE) was the data center sustainability metric. Used to measure the energy efficiency of a data center, PUE is calculated by dividing the total amount of energy used by the IT equipment energy used. The lower the PUE, the more efficient the data center’s energy usage. As data center users and operators became more comfortable bringing outside air into the facility, the thinking about energy efficiency evolved, and operators began to target—and reach—PUEs well under 1.5.

The focus on PUE in data center sustainability efforts has driven significant improvements in energy efficiency. But as it only covers mechanical and electrical efficiency, PUE was never intended to be a broad measure of carbon impact. Today, our data center sustainability efforts include PUE, as well as Water Usage Effectiveness (WUE), Carbon Usage Effectiveness (CUE), and data center greenhouse gas (GHG) emissions.