Summary
- Water UK's current average daily data centre demand estimate is around 6.6 million litres.
- Its 14 million-litre figure represents average peak demand, not normal daily consumption.
- Trebling capacity could increase average demand to 19.8 million litres and average peak demand to 42 million.
Full Fact has challenged the way headline figures for UK data centre water demand have been presented, pointing to a material difference between average daily consumption estimates and the much larger numbers modelled for periods of peak demand.
The distinction comes from written evidence submitted by Water UK. Its modelling puts current average daily water demand from data centres at approximately 6.6 million litres a day. If UK data centre capacity trebles by 2030, the corresponding average could rise to around 19.8 million litres.
The more widely quoted figures of 14 million litres today and 42 million litres by 2030 refer instead to average peak demand — the amount that could be required during hotter periods when cooling systems and the wider water network are under greater pressure.
Water UK also modelled a more severe case in which new facilities use relatively water-intensive cooling systems. Under that scenario, peak data centre demand could reach 77 million litres a day by 2030.
None of those figures is a simple forecast of annual water consumption. They describe different operating conditions and assumptions, which is important when the numbers are used in planning and public debate. Treating a peak-demand estimate as though it were the normal daily rate overstates routine use; focusing only on an annual average can understate the infrastructure challenge during hot, dry periods.
The water network has to cope with peaks as well as averages. A data centre that uses little or no potable water for cooling may present a relatively modest operational demand, while an evaporative cooling system can create a much larger requirement when ambient temperatures rise. The technology choice, local climate, workload, and facility design therefore determine far more than the label “data centre” alone.
Geography makes the issue more difficult. Water UK told Parliament that more than three quarters of UK data centres are in water-stressed areas in eastern and south-eastern England. Those are also regions where power, land, and connectivity have historically concentrated digital infrastructure.
The organisation said water companies had received individual requests of up to 21 million litres a day from data centre developers during the previous two years. A request is not the same as actual consumption, but figures of that scale can force utilities to examine whether local treatment, storage, mains, and abstraction systems can support a proposed development.
As higher-density AI systems increase cooling loads, the water question cannot be reduced to a single national litres-per-day number. Direct liquid cooling, for example, moves heat efficiently away from processors but does not by itself determine how the facility ultimately rejects that heat. A closed loop within the data hall can still connect to several different external cooling architectures, each with a different water profile.
The same distinction applies to water usage effectiveness. A low WUE figure provides useful information about operational water consumption, but it does not answer every local infrastructure question, including potable-water source, peak requirements, resilience arrangements, or competing demand during drought conditions.
Full Fact’s correction therefore does not show that water pressure around UK data centres is negligible. It shows that the figures need to be described accurately. Water UK’s own evidence still anticipates materially higher demand if capacity grows rapidly and highlights the concentration of facilities in stressed regions.
The planning question is more precise than the headline debate: what will a particular facility require on an average day, what could it require during a hot peak, where will that water come from, and can the local network provide it without shifting risk onto other users?
