660 Million Gallons Per Day
US data centres consume an estimated 660 million gallons of water per day for cooling — equivalent to the daily residential water consumption of a city of 4 million people. With data centre capacity projected to double by 2028, water consumption is on track to exceed 1 billion gallons daily.
This is no longer a sustainability talking point. It is a permitting constraint, a community opposition catalyst, and an operational risk in water-stressed markets.
How Data Centres Use Water
**Evaporative cooling (the primary consumer):** Most large data centres use cooling towers that reject heat by evaporating water. Warm water from the cooling system is sprayed over fill media while fans draw air across the surface. Evaporation absorbs heat, cooling the remaining water for recirculation.
- -Consumption rate: 1.8-4.0 litres per kWh of IT load (depending on climate and system efficiency)
- -A 50 MW facility in a hot climate: 3-7 million gallons per month
- -Annual consumption for a 100 MW facility: 50-150 million gallons
**Humidification:** Data centres maintain 40-60% relative humidity to prevent electrostatic discharge. In dry climates, humidifiers consume additional water — typically 5-10% of total facility water usage.
**Domestic and fire suppression:** Minor relative to cooling: restrooms, kitchen, and pre-action fire suppression system testing.
Water Usage Effectiveness (WUE)
WUE is the standard metric for data centre water efficiency, defined by The Green Grid:
WUE = Annual Water Usage (litres) / Annual IT Energy (kWh)
**Industry benchmarks:** - Best-in-class (water-free cooling): 0.0 L/kWh (WUE = 0) - Leading hyperscale: 0.2-0.5 L/kWh - Average colocation: 1.0-1.8 L/kWh - Older/inefficient facility: 2.0-4.0 L/kWh
**Reporting:** - Google reports fleet-wide WUE of 0.64 L/kWh (2024) - Microsoft reports fleet-wide WUE of 0.49 L/kWh (2024) - Meta reports fleet-wide WUE of 0.26 L/kWh (2024, reflecting heavy use of air-side economisation) - Most colocation providers do not publicly report WUE
Water-Free Cooling Alternatives
**Air-side economisation (free cooling):** Uses outside air directly (or through heat exchangers) to cool the data centre when ambient conditions permit. Zero water consumption during economisation hours. - Effective when outside air is below 27°C (80°F) and within humidity range - Hours of availability: 3,000-7,000 hours/year depending on climate - Nordic locations (Stockholm, Helsinki): 7,500+ hours/year (near-100% free cooling) - Phoenix, Arizona: 1,500-2,500 hours/year (supplemental only) - Capital cost premium: 10-15% over standard cooling tower systems
**Closed-loop dry coolers:** Reject heat through air-to-water heat exchangers without evaporation. Similar to a car radiator. - Zero water consumption - Less efficient than evaporative cooling in hot climates (approach temperature 8-15°C versus 3-5°C for cooling towers) - Requires larger heat exchanger surface area, increasing capital cost by 15-25% - Effective in moderate and cool climates; requires supplemental cooling above 35°C
**Liquid cooling (DLC and immersion):** By moving heat rejection to a closed-loop liquid system, facilities can use dry coolers for 100% of heat rejection. - Direct liquid cooling with dry coolers: WUE = 0 - Immersion cooling with closed-loop heat rejection: WUE = 0 - Capital cost premium: 20-40% over air-cooled with evaporative towers - Operating cost reduction: 30-60% lower cooling energy
**Adiabatic cooling (hybrid):** Dry coolers with mist-assist during peak temperatures. Water is consumed only during the hottest hours. - 70-90% water reduction versus full evaporative cooling - Effective compromise for hot climates where dry cooling alone is insufficient - Water consumption: 0.2-0.8 L/kWh (versus 1.8-4.0 L/kWh for full evaporative)
Regulatory and Permitting Impact
**Arizona:** - Chandler and Mesa require water usage reporting for data centres - Some jurisdictions require demonstration of 100-year water supply adequacy - Groundwater pumping restrictions in Active Management Areas - Operators increasingly required to purchase and retire water credits
**Texas:** - No statewide water restrictions for data centres (yet), but local water districts set allocation limits - San Antonio Water System (SAWS) has imposed tiered pricing that penalises high-volume users - Drought contingency plans may require curtailment of non-essential commercial water use
**European Union:** - Ireland: Data centres consumed 21% of national electricity in 2023, prompting water usage scrutiny alongside power - Netherlands: Amsterdam moratorium partially motivated by water usage concerns - EU Corporate Sustainability Reporting Directive (CSRD) requires water usage disclosure for large operators
**Community opposition:** Water consumption is the second most cited concern (after power grid strain) in community opposition to data centre development. In water-stressed markets, this single issue has blocked or significantly delayed projects worth billions.
Assessing Water Risk
When evaluating a data centre location for water risk, consider:
1. **Current water stress level:** The WRI Aqueduct tool provides water stress scores for any global location 2. **Projected future stress:** Climate models project increasing drought frequency in the US Southwest, Mediterranean, and parts of India and China 3. **Regulatory trajectory:** Is the jurisdiction trending toward more restrictive water policies? 4. **Alternative water sources:** Reclaimed/recycled water, rainwater harvesting, or municipal greywater can supplement or replace potable water 5. **Cooling technology choice:** Design for water-free or water-minimal cooling from the outset; retrofitting is expensive
Assess any location's water risk and environmental profile using the Score Tool. For sustainability-focused site selection, contact our advisory team.