Why Data Centers Use Water

Water is one of the most efficient and cost-effective mediums for removing heat. Many data center cooling systems use evaporative cooling, which works by evaporating water to absorb heat from the air or from cooling loops. When water evaporates, it absorbs a large amount of thermal energy, making it far more efficient at cooling than air alone. Cooling towers, the most common evaporative cooling system, are a familiar sight at large data center campuses.

The scale of water consumption is significant. A large data center might use several hundred thousand gallons of water per day for cooling, particularly in hot climates where evaporative cooling runs continuously during summer months. Google reported using approximately 5.6 billion gallons of water across its data center operations in 2023. Microsoft disclosed approximately 6.4 billion gallons. As the number and size of data centers grows, water consumption has become an increasingly scrutinized aspect of the industry’s environmental impact.

Water Usage Effectiveness

Water usage effectiveness, or WUE, is the standard metric for measuring data center water efficiency. Similar to PUE for energy, WUE is calculated by dividing the annual water usage of the data center by the total IT equipment energy consumption. The result is expressed in liters per kilowatt-hour. A lower WUE indicates more efficient water use.

Hyperscale operators report WUE values ranging from approximately 0.2 to 1.8 liters per kilowatt-hour, depending on climate and cooling technology. Facilities in cooler climates that can use free air cooling for most of the year consume far less water than facilities in hot, arid regions that rely on evaporative cooling year-round. Some facilities use closed-loop cooling systems that recirculate water without evaporation, dramatically reducing consumption but at higher energy cost.

The Controversy

Data center water consumption has become controversial in water-stressed regions. In Arizona, Oregon, and parts of the American West, communities have pushed back against new data center construction, citing concerns about water availability for residential and agricultural use. Several data center proposals have been modified or delayed in response to community opposition focused on water.

The issue is nuanced. While data centers do consume significant water locally, they often displace water consumption that would otherwise occur elsewhere. A cloud data center serving thousands of businesses might use less total water than those businesses would use running their own less-efficient on-premises servers. However, this argument provides little comfort to communities facing local water shortages.

Reducing Water Consumption

The industry is actively working to reduce water consumption through several approaches. Dry cooling systems use air-to-air heat exchangers instead of evaporative cooling, eliminating water consumption entirely. The tradeoff is higher energy consumption, since air is less efficient at heat removal than water. Hybrid systems use dry cooling when temperatures are moderate and switch to evaporative cooling only during the hottest periods.

Direct liquid cooling of servers eliminates the need for large-scale facility cooling systems, dramatically reducing both water and energy consumption. Some operators are using recycled water or non-potable water for cooling, reducing the demand on drinking water supplies. Others are investing in water restoration projects, returning more water to local watersheds than their operations consume. Both Google and Microsoft have committed to becoming water positive, replenishing more water than they consume, though achieving this goal at the pace of their expansion remains challenging.