What should accompany a PUE value?
Power Usage Effectiveness compares total data center energy with the energy used by IT equipment over a defined boundary and period. It helps show how much facility energy supports the IT load, but the number is meaningful only when the measurement method and context are stated.
ISO published ISO/IEC 30134-2:2026 in January 2026. ISO states that the edition includes updated measurement requirements and guidance for mixed-use buildings, unaccounted energy, and on-site generation.
- Measurement boundary and category
- Meter locations, coverage, accuracy, synchronization, and missing data
- Reporting period and whether the value is measured, estimated, instantaneous, or annualized
- IT load, occupancy, utilization, density, and major changes during the period
- Climate, operating conditions, cooling mode, and mixed-use building treatment
- On-site generation, exported energy, unaccounted energy, and any normalization
What does a low PUE not prove?
PUE does not by itself prove low carbon emissions, renewable energy use, water performance, IT efficiency, high utilization, good reliability, maintainability, security, appropriate temperature, or sustainable lifecycle decisions. A poorly utilized facility can report an attractive ratio while using more total energy than a better-utilized alternative.
How should an owner use PUE?
Use a consistent method to track the same facility over time, investigate changes, prioritize supporting-infrastructure improvements, and compare options only when the boundaries and conditions are sufficiently comparable. Pair PUE with absolute energy, IT service or workload measures, carbon, water, capacity, resilience, and operating-risk indicators.
Primary source: ISO/IEC 30134-2:2026. Source status checked 23 August 2026.