Data centers use an enormous amount of water for both on-site cooling and off-site electricity generation.

There are two related but different types of water usage — water withdrawal (a.k.a. water abstraction) and water consumption, both of which are important for holistically understanding the impacts on water stress and availability. Water withdrawal: It refers to freshwater taken from the ground or surface water sources, either temporarily or permanently, and then used for agricultural, industrial or municipal uses (normally excluding water used for hydroelectricity generation). Water consumption: It is defined as “water withdrawal minus water discharge”, and means the amount of water “evaporated, transpired, incorporated into products or crops, or otherwise removed from the immediate water environment”

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Scope 1 (on-site) water consumption

• Cooling towers: depending on the weather conditions and operational settings, data centers can evaporate about 1 – 9 liters per kWh of server energy (about 1 L/kWh for Google’s annualized global number and 9 L/kWh for a large commercial data center during the summer in Arizona.
• Outside air cooling with water assistance: Water consumption of 0.2 L/kWh averaged over Meta’s global data centers. Note that when the outside air temperature is high, outside air cooling evaporates a significant amount of water, thus resulting in a low average but high peak water withdrawal.

The US average WUE according to United States Data Center Energy Usage Report (2016) is 1.8 L/kWh.

The WUE coefficient for cooling should vary over time based on the outside temperature. Concretely, WUE increases significantly for cooling towers when the outside wet bulb temperature increases, and increases for outside air cooling when the outside dry bulb temperature is too hot or the humidity is too low.

Microsoft confirms this in How Microsoft measures datacenter water and energy use to improve Azure Cloud sustainability (2022): “[T]here are variables that can impact WUE—many of which relate to the location of the datacenter. Humid locations often have more atmospheric water, while arid locations have very little. Datacenters in colder parts of the world, like Sweden and Finland operate in naturally cooler environments so require less water for cooling. Our datacenter designs minimize water use. The chart below shows (in blue) our estimated or designed WUE figure, and in grey, our actual WUE figure. Again, Asia Pacific is higher due to higher ambient temperatures and as a result the need in some places for water-cooled chillers.” Microsoft’s WUE is 0.55 L/kWh in the Americas, 1.65 L/kWh in Asia Pacific, and 0.1 in EMEA.

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Scope 2 (off-site) water consumption

Per Water use of electricity technologies, Water consumption depends on the fuel source (coal, natural gas, biomass, nuclear) and the cooling mechanism (wet cooling, closed-loop cooling, etc). As examples, a closed-loop nuclear plant uses 2.5 L/kWh, whereas a once-through coal plant uses 0.4 L/kWh.

From EDF Lifecycle analysis of French nuclear plants (2022), the average WUE is 1.3 L/kWh.

For electricity generation, the U.S. national average water withdrawal and consumption are estimated at about 43.8 L/kWh and 3.1 L/kWh, respectively.

Similarly to scope 1, the WUE for the grid will vary based on the fuel sources used and by cooling factors like the temperature and humidity.

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Scope 3 water consumption

AI chip and server manufacturing uses a huge amount of water. For example, ultrapure water is needed for wafer fabrication, and clean water is also needed for keeping semiconductor plants cool. Overall, a large semiconductor plant may withdraw several million liters of water each day. Unlike scope-1 and scope-2 water usage, the data for scope-3 water usage (including withdrawal and consumption) remains largely obscure.

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Water use of electricity technologies

Yi Jin, Paul Behrens, Arnold Tukker, Laura Scherer. Water use of electricity technologies: A global meta-analysis

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Data Sources

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Water Use by Country and US Grid Region

Used in calculation defaults: Paul Reig, Tianyi Luo, Eric Christensen, and Julie Sinistore. WRI Guidance for Calculating Water Use Embedded in Purchased Electricity