Ask what a semiconductor fab consumes and most people answer “power.” That’s half the story. A leading-edge fab also runs on enormous volumes of ultrapure water — water cleaned far beyond drinking standard, used to rinse wafers between process steps.
The number that gets left out
Producing ultrapure water is itself water- and energy-intensive: a large fraction of incoming municipal water is lost in the purification process before a single wafer is rinsed. So the headline “gallons per wafer” understates the true withdrawal from the local basin.
That matters because fabs are frequently sited in regions chosen for tax, talent, or logistics — not for water. When the water math is done late, it’s done as a constraint, not a choice.
Water is rarely the reason a fab is sited somewhere. It’s increasingly the reason one can’t be.
The takeaway
Treat water as a first-class siting input, not a permitting afterthought. The basins that can absorb a new fab’s draw are a shorter list than the map of available industrial land suggests.
The full accounting — by node, by region — is in The Water Cost of AI.
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