What is WUE (ISO/IEC 30134-9)?
WUE, or water usage effectiveness, is a data center metric that relates annual site water use to the energy used by IT equipment, usually expressed in liters per kilowatt-hour. It was introduced by The Green Grid and is standardized as ISO/IEC 30134-9. It shows how much water a site uses to support its computing load.
What it is
Many data centers use water for cooling, through cooling towers, evaporative systems or humidification. WUE puts that water in the context of the IT work being supported.
Site water use typically includes make-up water to cooling towers and evaporative systems, humidification and other operational uses. A source-based variant can also include water used to generate the electricity the site consumes.
There is often a trade-off between water and energy. Evaporative cooling can lower PUE while raising WUE, so the two should be read together.
Where it is used
Data center operators, especially in water-stressed regions, use WUE to report to customers, investors and communities, and to design cooling strategies.
Campuses and industrial sites with large cooling loads use the same approach to track water per unit of output.
How it is measured
WUE needs metered water and metered IT energy over the same period.
- Cooling tower make-up and blowdown volumes
- Humidification and other process water
- IT equipment energy for the same period
- Water quality data that affects cycles of concentration
How Aqueduct helps
Aqueduct meters cooling make-up and blowdown into a balance, so WUE is measured rather than estimated.
- aQ WaterGuard balance across make-up, blowdown and evaporation
- WUE per site or hall alongside PUE
- Overflow, drift and leak detection on cooling systems
- Verified water reductions after changes to cooling operation