Voters rejected AI data centers over resource concerns. Here's why measuring water usage is hard

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Voters made it clear this week that they want to see limits put on data centers for artificial intelligence, passing 40 of 41 proposed ballot measures that would place restrictions on some of the more than 2,000 new facilities planned for communities around the nation.

Water and power top the list of ratepayers' concerns. But calculating how much each data center draws from local resources is an elusive task, with operators typically reporting usage figures companywide instead of site by site.

Giant 1-gigawatt AI data centers from the likes of Meta, Google, Amazon and SpaceX can consume up to 10 million gallons of water per day, according to Shaolei Ren, a data center researcher and professor at University of California, Riverside.

The exact number varies greatly depending on what type of hardware is inside a data center, where it's built, and what method is used to cool the servers and the building as a whole.

The complex ways data centers use water have left room for misinformation from both the builders and those fighting against them. CNBC talked to experts to get a clearer picture.

Air vs. liquid cooling

Data centers need serious internal cooling methods to keep chips and servers from overheating.

Legacy data centers, filled with lower-power servers used for things like networking or storage, are often air-cooled. Large fans move hot air away from the servers and outside the building.

But modern AI data centers are filled with high-power, denser graphics processing units, or GPUs, which Ren said can run so hot that the servers can "boil your eggs."

Water is about 3,000 times more efficient for cooling down these GPUs, according to Equinix sustainability head Christopher Wellise.

GPUs "run at such a high wattage, a high temperature, you would need nearly hurricane-force winds to actually cool them down if you were just using air," Wellise told CNBC in an interview.

Less water, more power

Creating cooler chips

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