What is power usage effectiveness (PUE)?

How it works

PUE is the total energy a data center draws divided by the energy consumed by its IT equipment. The Congressional Research Service lists that equipment as servers, data storage and communications gear. PUE is commonly reported as an annual average. A PUE of 1.0 would mean no energy goes to overhead such as cooling and power distribution. Google notes that at a PUE of 2.0, every watt of IT power is matched by another watt for cooling and power distribution.

The Green Grid introduced the metric in 2007, according to the Uptime Institute. An international standard, ISO/IEC 30134-2, now sets out how to measure, calculate and report it. A second edition published in January 2026 replaced the 2016 one. ISO says it adds guidance on mixed-use buildings and on-site generation.

What it does not tell you

Uptime has collected PUE figures from operators since 2007. Its 2026 survey report notes that water consumption and IT energy efficiency fall outside the metric. It adds that climate, resiliency goals and business objectives influence the result. Uptime considers PUE best suited to tracking one site over time or trends across large samples, not to comparing a few different facilities.

Where things stand in 2026

Uptime's 2026 survey, published in July, put the industry average at 1.52, compared with 2.50 in 2007 and 1.54 in 2025. It described the figure as largely flat over seven years. An Uptime calculation published in August 2026 that gives larger facilities proportional weight produces 1.36. Google reports a fleet-wide PUE of 1.09 for the twelve months through the second quarter of 2026. The company calculates that figure itself.

A 2024 EU regulation covers data centers with at least 500 kilowatts of installed IT power demand. Their operators must report energy data to a European database every year. PUE is calculated from that data. In September 2026 the European Commission adopted a regulation creating a common rating scheme for data centers, pending two months of scrutiny by the European Parliament and Council.

Germany's Energy Efficiency Act requires data centers that begin operating on or after July 1, 2026 to reach a PUE of 1.2 or lower within two years of commissioning. A government bill would extend that period to four years. It had its first reading in the Bundestag on September 24, 2026, followed by a committee hearing on October 5, 2026.