PUE (Power Usage Effectiveness)

PUE (Power Usage Effectiveness) is a ratio that measures data center energy efficiency by dividing total facility power by the power delivered to IT equipment. A PUE of 1.0 would mean every watt goes to servers; the difference is consumed by cooling, power conversion losses, and lighting. The Uptime Institute's global survey puts the industry average around 1.56, while hyperscale operators like Google report fleet-wide PUE near 1.10. Modern colocation facilities typically advertise design PUE of 1.2-1.4; older enterprise data centers often run above 1.8. PUE is defined in ISO/IEC 30134-2 and is the most widely quoted efficiency metric in colocation contracts and sustainability reports, though it says nothing about water use or IT hardware efficiency.