DEFINITION
A sustainability metric defined by The Green Grid that measures how much water a data center uses for cooling and other building needs relative to IT energy consumption.
Water Usage Effectiveness (WUE) is a metric created by The Green Grid to help data centers measure and monitor their water consumption. It is calculated by dividing the annual site water usage (in liters) by the IT equipment energy usage (in kilowatt-hours).
WUE = Annual Water Usage (L) / IT Equipment Energy (kWh)
Benchmarking
- Excellent: WUE < 0.2 L/kWh
- Average: WUE ~ 1.8 L/kWh (Typical Cooling Towers)
- Poor: WUE > 2.5 L/kWh
Trade-off with PUE
There is often an inverse relationship between Power Usage Effectiveness (PUE) and WUE. Evaporative cooling improves PUE by reducing compressor load but increases WUE. Modern facility design requires a careful balance based on local water availability versus energy costs.