How much water will the site need on its busiest day?
Ask about water use on the busiest day, not only the yearly average.
Your town’s water system must be ready for the site’s busiest day, not just an average day. The hottest days matter. So do the water source and the local supply.
A site with a closed loop can still evaporate water in a cooling tower.
Sources: US Department of Energy, Federal Energy Management Program, Cooling Water Efficiency Opportunities for Federal Data Centers, accessed November 11, 2026; Memphis Light, Gas and Water (copy on the City of Memphis website), MLGW Utility Support to xAI (committee presentation), July 9, 2024.
What good looks like
- The design to save water covers the whole campus, including cooling in hot weather.
- A local study of the water supply covers the highest demand and drought.
- Once the site runs, dated meter readings replace forecasts.
What to watch for
- The cooling evaporates water. It draws heavily on a local supply that is already tight.
- The water figure covers only one building or one cooling loop.
- A claim to replenish water is put forward as proof of no local problem.
Where to look
- Water-utility capacity study or service agreement The utility’s study of how much water it can supply, or its contract to serve the site.
- Cooling-system description and site plans How the site will be cooled, and drawings of what will be built.
- Water permit and dated operating reports The permit for the site’s water, and dated reports from the running site.
In Virginia, some buildings used less water than a typical household. One used 243 million gallons in a year.
Some buildings
Less than a typical household
The report gives no number for a typical household.
Most buildings
About 6.7 million gallons a year, or less
The report compares this to an average large office building.
11 buildings
Over 50 million gallons each
One building
243 million gallons
The report says this was 10 percent of the water used by all data centers in the state.
Million gallons a year, per building, Virginia, 2023
Measured result
Source: Virginia Joint Legislative Audit and Review Commission (JLARC), Data Centers in Virginia (Report 598), December 9, 2024.
Microsoft says over 90% of capacity at its Mount Pleasant site reuses the same water. The rest uses water only on the hottest days.
Capacity on the closed loop
Over 90%
Microsoft says this system needs water only once, during construction. It says the water is reused with no evaporation losses.
Traditional servers
The remaining 10%
Microsoft says these use outdoor air for cooling and switch to water only during the hottest days.
Water on the hottest days
No amount given
Company statement
Source: Microsoft (Official Microsoft Blog), Inside the world’s most powerful AI datacenter, September 18, 2025.
The trade-off
Cooling choices can move demand from water to electricity, or the other way. Check both for the local climate and the site.
Does a public record for this project give a water estimate for the busiest day (the “peak day”)?
- Yes
- A source gives a peak-day estimate as a number, for the phase you are checking. This does not prove the supply is enough.
- No
- A source says outright that no peak-day estimate has been prepared for that phase.
- Not known
- You found only averages, company-wide totals, a source you could not open, or no clear answer.
Two real projects
Lighthouse — Port Washington
Port Washington, Wisconsin
Is a number public for how much water the site or campus needs or consumes?
YesCompany statement
The city’s release of March 19, 2026 gives a forecast for a day when water use is highest (a “peak day”). The forecast is about 22,000 gallons. Separately, the Public Service Commission of Wisconsin (PSC) records a daily demand of 22,000 gallons. The applicant stated that figure. The PSC record sets it apart from fire-flow capacity, the water flow needed to fight a fire. These are planning figures, not use measured by a meter.
Sources: City of Port Washington, City amendment of construction hours and project financing update, March 19, 2026; Public Service Commission of Wisconsin, Port Washington water main: docket 4780-CW-105, July 2026.
Google — The Dalles campuses
The Dalles, Oregon
Is a number public for how much water the site or campus needs or consumes?
YesMeasured result
The April 2023 water profile reports water consumed (used and not returned) in The Dalles in 2021. The figure is almost 275 million gallons. It is from the past and covers the local campuses together. It is not a current figure for a day when water use is highest (a “peak day”).
Source: Google, The Dalles water profile, April 2023.