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Glossary
Data centers

What is WUE (ISO/IEC 30134-9)?

Definition

Water usage effectiveness (WUE) is the ISO/IEC 30134-9 key performance indicator for the water a data centre consumes while operating, reported as the water intensity of running the facility.

Who reports it and why

Operators of evaporatively cooled and water-cooled data centres report WUE, often because hyperscale and colocation customers ask for it. Location sharpens the issue: 25 countries holding a quarter of the world's population face extremely high water stress, per WRI Aqueduct 4.0.

What the standard defines

ISO/IEC 30134-9 was published in March 2022 as Part 9 of the data centre KPI series. It defines WUE, introduces measurement categories, relates the KPI to infrastructure, IT equipment and IT operations, and sets rules for measuring, calculating, reporting and interpreting it. ISO lists it as due for revision, so confirm the edition before reporting.

Metered water for the numerator

WUE needs metered water, not a bill split evenly by month. Aqueduct meters each line on the water twin, such as cooling tower makeup, RO feed and reject and reclaimed flow, and the water balance equation's unaccounted loss term exposes water leaving the site with no metered destination, which would otherwise inflate the ratio.

Questions

WUE (ISO/IEC 30134-9): common questions

WUE is the standardized metric for how much water a data centre uses to run, defined in ISO/IEC 30134-9. It relates site water consumption, mostly for cooling, to IT energy, giving operators and customers a way to track water intensity. Aqueduct's view is on the data centers page.

Both come from the ISO/IEC 30134 series and are read together, since cooling choices that cut energy overhead often use more water. A site reporting only PUE can look efficient while its water use climbs.

The ISO standard is voluntary. Any obligation comes from a regulator, permit or customer contract that references it. Customers increasingly ask colocation providers for WUE, especially in water-stressed regions, so many operators report it before any rule requires them to.

Meters on every water input used for operations, such as cooling tower makeup, humidification and treatment plant feed, plus metered IT energy. Aqueduct records each line and shows unaccounted flow, so the reported water figure matches what the site actually consumed, as covered under water outcomes.

See Aqueduct on your own facility.

Bring a site, a utility bill or a question. We will show you where the loss is.

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