Water Usage Effectiveness (WUE): How Data Center Water Use Is Measured

WUE is the water counterpart to PUE. The Green Grid introduced it in a March 2011 white paper as a data center sustainability metric, alongside its carbon metric (CUE).¹ The idea is simple: divide the water a facility uses over a year by the energy its IT equipment uses over the same year.

The metric is now an international standard. ISO/IEC 30134-9:2022 specifies WUE as a key performance indicator for the water consumption of a data center during its use phase, and covers how to measure, calculate and report it.² Expressed as a formula, WUE is the ratio of data center water consumption in liters to IT equipment energy in kilowatt-hours, so the unit is liters per kWh (L/kWh). A lower value is better; a value close to zero means negligible water use.⁷

WUE says nothing about where the water comes from. A liter of reclaimed wastewater counts the same as a liter of potable water or groundwater, so WUE should always be read with the source, as our guides to reclaimed water and water rights and groundwater explain.

Two published WUE figures can describe very different things. The first distinction is scope. Site WUE counts only water used at the data center. Some operators also report, separately, the water used off site to generate the electricity the facility consumes. That indirect share is large. Berkeley Lab estimated that U.S. data centers consumed about 17 billion gallons (64 billion liters) directly in 2023 and about 211 billion gallons (800 billion liters) indirectly through their electricity.⁹¹⁰

The second distinction is withdrawal versus consumption. Withdrawal is all the water taken in; consumption is the part that evaporates or otherwise does not return. WUE can be reported on either basis.⁸ Microsoft’s published figure is a withdrawal WUE.³ Amazon defines its WUE as the volume of water withdrawn per kWh of IT load.⁴ A cooling tower that discharges blowdown to sewer has a withdrawal WUE well above its consumption WUE, so the two should not be compared directly.

Metering adds another wrinkle. Most facilities have one central water meter, so reported totals often include domestic and landscaping water along with cooling.¹⁵ A fleet average can also hide one water-intensive site in a dry market.¹⁵

Large operators publish fleet and regional averages, but the range is wide. Microsoft reported a fiscal 2024 global average withdrawal WUE of 0.30 L/kWh, a 39% improvement from 0.49 L/kWh in 2021, which it attributes to reducing water waste, widening operating temperature ranges and auditing operations.³ Amazon reported a 2024 average of 1.68 L/kWh in Singapore and 1.57 L/kWh in 2025, noting that it operates all of its Singapore data centers on NEWater, the country’s reclaimed water.⁴ Data Center Knowledge cites an industry-wide average of about 1.8 L/kWh.¹⁵

Design matters more than any single number. EPRI models a 150 MW data center with a water-cooled chiller plant at 2.8 L/kWh, and a similar-sized facility with IT liquid cooling and dry coolers at 0.2 L/kWh, about 190,000 gallons a day.⁵ Microsoft says all new data center designs since August 2024 use a closed-loop cooling system that, once filled during construction, recirculates without additional water, saving more than 125 million liters per data center each year; pilots are planned in Phoenix and Mt. Pleasant in 2026, with sites coming online from late 2027.³ Its existing fleet will keep a mix of air- and water-cooled systems for years.³ Our guide to closed-loop and waterless cooling covers the trade-offs.

In the EU, Delegated Regulation (EU) 2024/1364 requires larger data centers to report key performance indicators, including total water intake, to a European database, and defines four sustainability indicators: PUE, WUE, the energy reuse factor and the renewable energy factor.¹¹ The 2024 rules are reporting-only, with no minimum performance levels.¹¹ In 2026 the European Commission published a draft amendment to create a mandatory EU-wide sustainability rating and label for data centers, with a revised draft issued on July 2, 2026.¹¹ The Commission adopted the delegated act in September 2026 and sent it to the European Parliament and Council for a two-month scrutiny period; it is also consulting on possible minimum performance standards.¹⁶ The annex assigns water classes from A (WUE of 0.1 or less) to G (above 1.0).¹² As of October 2026, confirm that the act has entered into force and when the first labels are due.

U.S. rules are mostly state-level and new. Utah’s Division of Water Rights requires reporting from new data centers larger than 10,000 square feet that intend to draw 75 acre-feet or more of water a year, effective July 1, 2026.¹³ Operators file a pre-construction report with estimated annual withdrawal and reuse plans, then annual reports of actual withdrawals; the state publishes the reports each September.¹³ California went further in September 2026, when Governor Newsom signed AB 2619 as part of a package of data center bills; it requires an operator to give its water supplier an estimate of expected water use before applying for an initial local business license and to report actual use at renewal.¹⁴ Other states have considered similar bills, so check the current session in the state where a site sits.

For a developer, these rules mean projected water use and WUE are becoming public records. Expect water utilities, counties and neighbors to ask for them early, as covered in our guide to municipal water and sewer capacity.

WUE is useful on a site because it converts IT load into an annual water volume. The arithmetic: IT load in kW × 8,760 hours × utilization × WUE = liters a year. At 100 MW of IT running at an average 80% and a WUE of 1.2 L/kWh, that is about 840 million liters (220 million gallons) a year, or roughly 600,000 gallons a day on average. These numbers are illustrative.

Averages understate what the utility has to deliver. A study of data center demand on public water systems used a planning WUE of 1.2 L/kWh and estimated that an evaporative system serving a 100 MW IT load would need a peak withdrawal capacity of about 2.5 million gallons a day, and possibly more than 5 million in hotter climates.⁶ Water mains, wells and treatment plants are sized on the peak day, and so are the wastewater connections that take cooling tower blowdown.

1. 01Ask the end user or designer for both annual WUE and peak-day water demand, and on which basis (withdrawal or consumption) they are stated.⁸
2. 02Confirm the source: potable, groundwater, surface water or reclaimed, and the permits each requires.
3. 03Check local drought and supply risk; see water stress and drought risk.
4. 04Check state reporting rules that may make the numbers public before construction.¹³¹⁴
5. 05Compare the water-heavy and dry-cooled designs on both water and peak power, since the trade-off runs both ways.⁵

Our guide to data center water requirements covers cooling choices in more depth. BlackForge screens water supply, wastewater capacity and power together; you can get a site reviewed.