The debate over data centers’ water use tends to focus on how much is needed to cool servers on-site. But that fails to capture the largest and least visible part of their overall use: the water used at the power plants fueling data centers’ rising energy needs.

Only one hyperscaler, Meta, reports its indirect water consumption embedded in purchased electricity. That figure was more than 20 times higher than the amount of water directly consumed by its data centers in 2024 — and grew every year since 2021, according to Meta’s most recent sustainability report.

Meanwhile, Amazon told Latitude Media that it tracks indirect water consumption from power generation, but hasn’t publicly disclosed the data yet because there isn’t an industry-wide reporting standard. That leads to widely variable figures, depending on what assumptions are used, so the company is working with experts to develop a more consistent framework. (Neither Google nor Microsoft said whether they track indirect water use.)

A new analysis by the sustainable investment group Ceres attempts to help fill the gap. Ceres modeled data centers’ indirect water use across seven states — Arizona, California, Georgia, Illinois, Ohio, Texas, and Virginia — which combined are home to about half the data centers in the U.S. The report estimates that these data centers collectively used about 3.4 trillion gallons of freshwater in 2024 for electricity, or about or 12 times the combined total of Los Angeles, Phoenix, and Washington, D.C.