A Temperature That Breaks Intuition

Hot tubs run around 38 to 40 degrees Celsius. Nvidia’s newest AI servers run their cooling liquid even hotter, up to 45 degrees Celsius. That number sounds wrong at first. Hotter coolant should mean worse cooling, not better. The opposite turns out to be true. The coolant itself is unremarkable chemistry. It is a mixture of 75% water and 25% propylene glycol, a formulation similar to antifreeze. What changes everything is the temperature ceiling. The liquid enters at temperatures of up to 113 degrees Fahrenheit and exits at about 131 degrees Fahrenheit, once it absorbs the heat generated by the chips. Heat transfer follows simple physics. Warmer fluids release heat faster into outdoor air. Consequently, the warmer the coolant is when it reaches the outdoor radiator, the easier it becomes for passive cooling to work. That single insight reshapes facility design entirely.

Why Chillers Become Optional

Mechanical chillers exist for one reason. They artificially lower water temperature before it reaches outdoor air. Removing that requirement removes an enormous energy burden. Traditional water-cooling methods, especially those that use chillers, often account for nearly 40% of a data center’s power consumption. That figure explains the urgency behind this shift. Cooling has quietly become one of the most expensive line items in any AI facility. Outdoor dry coolers now handle what chillers once did. At 45C, it is warm enough to reject heat efficiently in the right climate without ever turning on a mechanical chiller. Engineers call this approach dry-cooler-based design. It relies entirely on ambient air, not refrigeration cycles. Nvidia’s own framing reinforces the scale of savings. Industry estimates suggest that increasing chiller temperatures by just 1.8 degrees Fahrenheit can reduce cooling energy costs by four percent. A jump from roughly 24 to 45 degrees Celsius compounds that effect dramatically.

The Geography Problem Nobody Skips

This breakthrough is not universal, however. Climate still governs whether chillers disappear entirely. The system can run without chillers only if outdoor air temperatures stay well below the coolant’s 45-degree limit. Phoenix illustrates the limitation clearly. Nvidia admits that data centers in very hot places like Phoenix, Arizona, may still need chillers during the hottest days of the year. Desert heat simply outpaces even generous coolant tolerances. Even Nvidia’s own engineers acknowledge this nuance. In the right geography, somewhere with reliably cool outdoor air, a liquid-cooled data center can reject its heat through coolant distribution units that capture heat directly at the source. “Right geography” carries real weight in that sentence. Vertiv, a major cooling infrastructure provider, pushed back gently too. Using higher-temperature water does not eliminate the need for heat rejection. While approaches to heat rejection may change, cooling infrastructure is still required. Chillers shrink. They do not vanish everywhere.

Water Savings That Sound Almost Unbelievable

Beyond energy, the water story grabbed even more attention. Conventional cooling-tower-based systems consume roughly 2.6 million gallons of water per megawatt per year, according to the company. That baseline makes any reduction newsworthy. Nvidia’s claim goes further still. Nvidia says the new design can reduce that figure to near zero. Closed-loop circulation explains why. The propylene glycol and water mixture is introduced into the system a single time and kept in circulation indefinitely. Microsoft made a remarkably similar claim around the same moment. Speaking at Microsoft Build 2026, Nadella said the daily water usage over the course of an entire year is roughly equivalent to what a single restaurant would use. Both companies are now racing toward identical messaging. Fairwater backs this up architecturally. Over 90% of the facility’s cooling relies on a closed-loop liquid cooling system that is filled during construction and then continuously recirculates the same water. The remaining cooling load uses outside air, not evaporation.

The Math That Stops at the Wall

Here is where the celebration deserves scrutiny. Both companies measure water at the facility boundary. Nothing upstream gets counted. Critics noticed quickly. Water consumed by power plants supplying the data center’s electricity, which Nvidia does not count in its figures, can double or triple a facility’s total water footprint. That gap is not trivial. It is the entire other half of the equation. Specific numbers make this concrete. For every kilowatt-hour produced, natural gas plants draw down 1.17 liters of water, while coal-fired generation is more demanding still, at 2.2 liters per kilowatt-hour. An AI campus drawing hundreds of megawatts generates enormous indirect consumption. Independent analysis confirms this asymmetry sharply. On-site cooling accounts for only about 4% of the additional water AI will demand through 2050, according to a 2026 analysis by Xylem and Global Water Intelligence. Ninety-six percent sits elsewhere, uncounted by either company’s headline claims.

Drought Maps Make This Personal

Geography turns this abstraction into something tangible. Many AI campuses sit precisely where water already runs short. The scale is striking. Two-thirds of the 809 data centers currently planned across the United States are located on land that has been in drought over the past year. Closed-loop cooling helps less when regional water systems are already strained. Arizona shows this tension sharply. The Bureau of Reclamation declared a Level 1 Shortage Condition on Lake Mead for 2026, requiring Arizona to cut approximately 18% of its annual water apportionment. That is the same desert region drawing major AI investment. Power generation, not server cooling, drives most regional strain. Fossil fuel power plant water demand represents roughly 54% of AI’s total projected water footprint through 2050, entirely unaddressed by closed-loop facility cooling. The chiller disappeared. The bigger draw did not.

The Honest Verdict

None of this makes Nvidia’s engineering hollow. NVIDIA’s water-free cooling is a genuine technical achievement. The engineering checks out. The efficiency gains are real. Removing chillers genuinely cuts both energy and on-site water dramatically. Still, language matters enormously here. Calling a facility “zero water” while ignoring upstream generation misleads the public. Both Nvidia and Microsoft made claims that are accurate yet incomplete simultaneously. Genuine accountability requires full-chain accounting. Operators should disclose generation-source water alongside facility-level figures. Anything less repeats a familiar industry pattern: solving the visible problem, leaving the larger one in shadow. The air-conditioned data center really is ending. Whatever replaces it deserves an honest ledger, not just a warmer thermostat.