Why AI data centre water use is hard to pin down: closed liquid loops use little water, but heat rejection on hot days can use a lot

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CNBC explains that most large AI data centres cool their GPUs with closed-loop liquid systems that use very little water day to day, but total water use depends on how the heat is rejected outdoors. Dry coolers use far less water but more power in hot weather, while evaporative cooling uses little power and loses water through evaporation, and hybrids switch between the two. Meta told CNBC that its 1 GW campus in Lebanon, Indiana will use zero water for most of the year, though the site's allocation could rise to 8 million gallons a day by 2031 for peak hot days. CNBC quotes University of California, Riverside researcher Shaolei Ren as saying 1 GW AI campuses can use up to 10 million gallons a day, and notes that Equinix's operations used 1.2 billion gallons in 2025. Figures are as reported and most operators do not publish site-level water use.

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