The short answer
Modern designs can substantially reduce cooling water demand. The result depends on the complete system, local weather, operating load, and what is included in the measurement.
1 / How heat leaves the equipment
| Method | How it collects heat |
|---|---|
| Air cooling | Fans move air across equipment and carry heat to the room’s cooling system. Air-cooled servers can still be served by a water-using cooling plant. |
| Direct-to-chip liquid cooling | Coolant flows through cold plates at heat-producing components. Other components may still need air cooling. |
| Immersion cooling | Equipment sits in an electrically insulating liquid that carries away heat. The fluid and system design determine how that heat moves onward. |
Sources: ARPA-E: COOLERCHIPS · DOE: Energy-efficient data center design guide (PDF)
2 / How heat leaves the facility
| Method | Water and operating considerations |
|---|---|
| Dry cooling | Transfers heat to outdoor air without intentionally evaporating water. Performance depends on outdoor and coolant temperatures. |
| Evaporative cooling | Uses evaporation to reject heat. Replacement water also covers losses such as blowdown, the water discharged to control mineral buildup. |
| Hybrid cooling | Combines dry and evaporative operation. Annual use depends on when and how often the wet mode runs. |
| Chilled water / refrigerant systems | These move heat between stages. A chiller may reject heat through air or through water-cooled equipment; “chilled water” alone does not specify the final water demand. |
Sources: DOE / NREL: Hybrid cooling case study (PDF) · DOE: Cooling tower management · DOE: Energy-efficient data center design guide (PDF)
Where large water savings come from
Using dry heat rejection for more operating hours can reduce reliance on evaporation. Better airflow and temperature controls can reduce unnecessary cooling demand. Cooling-tower management can reduce avoidable discharge. The right combination depends on the site.
One documented example: DOE’s 2019 case study reports that a hybrid installation at NREL’s Colorado high-performance computing facility cut data-center water use in half over the reported two-year period. That is a result for that installation, not a forecast for every campus.
Sources: DOE: Cooling water efficiency opportunities · DOE: Cooling tower management · DOE / NREL: Hybrid cooling case study (PDF)
Has water use dropped everywhere?
No. Better efficiency at individual facilities does not prove that total industry water consumption is falling. Berkeley Lab’s 2024 U.S. report estimates rising aggregate direct water consumption over 2014–2023 as demand expanded.
Water usage effectiveness (WUE) relates site water use to IT electricity use, commonly in liters per kilowatt-hour. A lower ratio can coexist with higher total water demand if total IT electricity consumption increases. Report both the ratio and the total volume, with matching boundaries and periods.
Sources: Berkeley Lab: 2024 U.S. Data Center Energy Usage Report
Read the water claim carefully
Withdrawal is water taken from a source. Consumption is the portion evaporated or otherwise unavailable for immediate use. Neither term should be silently substituted for the other.
A useful disclosure also identifies potable or reclaimed supply, annual and peak-day demand, local constraints, and whether water associated with electricity generation is included. Reclaimed water can reduce potable demand without eliminating water consumption.
Sources: USGS: Water-use terminology
For a specific campus
Ask for the selected cooling configuration, weather assumptions, operating load, water source, and measurement plan. These explainers describe available technologies; they do not announce an equipment selection or a verified water result for a TDC campus.
A question about a project?
Tell us which location or statement you’re asking about. Specific questions deserve specific evidence.
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