WUE
WUE is the ratio of annual water consumption to IT energy consumption — the standard water-side companion to PUE.
Definition
Water Usage Effectiveness (WUE) is the ratio of annual site water consumption (in liters) to the IT equipment energy consumption over the same period (in kWh). It is published as L/kWh.
WUE captures the water cost of operating the facility — primarily evaporative cooling, but also makeup water for chilled-water systems and any humidification. Facilities using closed-loop cooling and minimal evaporative makeup can run WUE values approaching zero. Facilities that lean heavily on evaporative cooling for low PUE can run WUE values of 1.0 L/kWh or more.
PUE and WUE are linked — most low-PUE strategies depend on evaporative cooling, which raises WUE. Operators in water-stressed regions are increasingly required to report WUE alongside PUE, and a number of jurisdictions are beginning to legislate water consumption disclosure for data center facilities.
WUE is part of the same standards family as PUE (ISO/IEC 30134-9) and is reported under the same caveats: measurement boundary, frequency, and load profile all matter when comparing facilities.
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