Water & Cooling Guide
How data centers stay cool — and how much water that takes
Plain-language explanations of common cooling approaches. We distinguish water withdrawn from water consumed and never fill missing water-use data with invented numbers.
Withdrawn vs. consumed: Water withdrawn is taken from a source and largely returned. Water consumed is evaporated or otherwise not returned. Figures should always state gallons/liters, the time period, location, and measurement boundary.
Air Cooling
Uses fans, CRAC/CRAH units, and chillers to move heat with air. Can use outside air (free cooling) in cool climates. Generally higher energy use than evaporative in hot climates, but minimal on-site water consumption.
Water withdrawn
Low
Water consumed
Low
Strengths
- • Minimal on-site water use
- • Simpler water permitting
Trade-offs
- • Higher energy use in hot climates
- • Larger equipment footprint
Water
Water Use at Data Centers
Data centers can use water in two main ways: directly for cooling (most often evaporative cooling), and indirectly through the water used to generate the electricity they consume. A critical distinction is water *withdrawn* (taken from a source and largely returned) versus water *consumed* (evaporated or otherwise not returned). Figures cited in the media often blur this distinction. Reliable, facility-level water data is scarce because disclosure is inconsistent. Where a figure is not publicly reported, we say so rather than estimate.
Cooling
How Data Centers Are Cooled
Servers generate heat that must be removed. Common approaches include air cooling (fans and chillers), evaporative cooling (using water evaporation, which consumes water but can save energy), direct-to-chip liquid cooling, and immersion cooling (submerging hardware in dielectric fluid). Some facilities reuse waste heat for district heating. Each approach trades off energy use, water use, and cost differently.