How Much Water Do Data Centres Really Use?

The short answer

A single large data centre can use millions of litres of water per day — roughly what a town of 30,000 to 50,000 people uses. Most of it is evaporated in cooling towers, which means it's gone for good, not returned to the system.

Why so much?

Servers generate intense heat, and that heat has to go somewhere. The two main cooling methods:

• Evaporative cooling (wet cooling): water is evaporated to pull heat away — extremely effective, extremely thirsty.
• Air / closed-loop cooling: fans and refrigerant move heat to radiators — uses little or no water, but uses more electricity.

Many facilities run a mix, and the exact figure depends on design, climate and server density.

Why it matters

The controversy isn't just the volume — it's where the water comes from. Data centres are often built in regions chosen for cheap power and land, which are frequently the same regions under water stress. Local residents see watering restrictions while a cooling tower evaporates millions of litres next door. That contrast drives a huge amount of the anger in both the US and the UK.

What to check in a planning application

• The daily water demand figure (usually in the environmental statement).
• Whether the design uses wet or dry cooling — and why.
• Where the water supply is coming from, and whether that's sustainable in drought years.
• Whether water reuse is proposed (some modern designs recycle most of it).

What good looks like

Some operators are switching to water-free or low-water cooling, using recycled wastewater, and publishing transparent water metrics. That's the standard communities should be demanding — and the minimum that should be written into planning conditions.

Part of the Brightfull Tech network. Contact: hello@brightfull.tech