Running the coolant hotter makes an AI data centre use less water, according to modelling published by Schneider Electric and reported by The Register on Monday.
The work is set out in a white paper titled "Water Usage at AI Scale: Insights from a 100 MW Comparative Analysis". It models a 100 MW facility in two locations, Paris and Dallas, under four designs.
Those designs are traditional air cooling, liquid cooling with coolant at 32C, liquid cooling at 45C, and an optimised 45C system with a reduced equipment count.
In Dallas, the modelling found that moving from air cooling to liquid cooling with 45C coolant cut water consumption by at least half.
The reason is what the heat is rejected into. Cooling towers work by evaporating water, and consume between five and twenty times more water than dry coolers for equivalent facility sizes. Dry coolers reject heat to the air, and only become practical once the coolant is warm enough to be cooled by ambient air alone.
Early AI data centres tended to run coolant at around 32C, about 90F. The optimised designs in the paper run at 45C, or 113F.
The context is a rising number. Water consumption by data centres in the United States has tripled over a decade, a trend that has made the industry's draw on municipal supplies a live planning question in several markets.
Schneider has an interest in the answer. The company took a 75 per cent controlling stake in the liquid cooling specialist Motivair in 2024 and has said it intends to buy the remainder by 2028. The Register noted that it has skin in the game.
Read literally, however, the finding is more interesting than a cooling recommendation, and this newspaper intends to read it literally.
The water is not being saved. It is being declined. A facility that evaporates water is one that has been asked to hold a lower temperature than it strictly requires, and the saving comes entirely from lowering that expectation by thirteen degrees.
Thirst, on this evidence, is not a property of the machine. It is a property of the operator's comfort, expressed through a thermostat and settled in a municipal water account.
The implication scales cleanly. Every additional degree the industry is prepared to tolerate is a quantity of water it no longer has to boil off into the sky above Dallas. There is no engineering limit in the argument, only a willingness limit.
The Department of Unnecessary Research has extended the model to its conclusion. The saving exists because the coolant is warmer than the air being used to cool it, which means the cheapest cooling system yet identified is a data centre that has been left warm enough to look after itself. The Department has forwarded the analysis to its own building manager, who has not replied.