Europe's demand for data centre capacity is growing rapidly, driven by AI, digitalisation, and government targets. The European Commission aims to triple EU data centre capacity by 2035, while the UK government forecasts a need for at least 6 GW of AI-capable capacity by 2030. As more facilities are built, their water requirements are coming under closer scrutiny. "Alongside electricity, water will increasingly determine where and how data centres can be operated economically and sustainably," said Mathias Franke, Head of Data Centre Consulting at Drees & Sommer.
Quantifying the actual water footprint of data centres remains difficult. Since 2024, EU reporting obligations have required facilities to disclose water use and Water Usage Effectiveness (WUE), yet the European Commission estimates that only around 50% of data centres subject to those requirements had reported by 2026. The International Energy Agency estimates that data centres required more than 500 billion litres of water in 2023, of which around 140 billion litres were used directly on site and approximately 373 billion litres were linked to electricity generation. Reported WUE values range from close to zero for some dry cooling systems to more than 2 litres per kilowatt-hour annually for evaporative systems. "There is no single best cooling solution," said Franke. "What works depends on the local climate, water availability, electricity mix, load profile, and opportunities to use waste heat."
The European Commission has proposed a common EU-wide rating scheme covering individual data centres with a capacity above 500 kW, with the first sustainability labels expected in 2027. The proposed Cloud and AI Development Act also links support and simplified permitting to water-efficiency requirements. International cases illustrate how water can become a planning obstacle: in Belgium, the Walloon government rejected Google's proposal to replace an approved air-cooling system with river-water cooling at a facility in Farciennes, citing recurring droughts and the need to protect regional water resources.
The incampus technology park in Ingolstadt, Germany, developed by Audi and the city administration on a 75-hectare former refinery site, shows how cooling, energy provision, and waste heat can be designed as an integrated system. Because residues in the soil require continuous groundwater extraction and treatment through ten wells pumping up to 200 cubic metres of contaminated water per hour, the project repurposes that extracted water for cooling via heat exchangers. The water remains part of the local water cycle and provides around 1.5 megawatts of heating and cooling capacity. The on-site data centre, operating since 2022, feeds its waste heat into a low-temperature network, with heat pumps and thermal storage units balancing continuous heat generation against fluctuating demand.
Drees & Sommer provided commissioning management services and supported integration testing across the data centre, pumps, heat exchangers, heat pumps, storage facilities, and distribution network. "In the past, building plots, electricity, and fibre connections were the key location factors. Today, we also need to determine which cooling system is best suited to local water conditions, whether it will still be viable in ten or twenty years, and how waste heat can be put to productive use," said Peter Junker, Associate Partner at Drees & Sommer. "This means looking beyond the site boundary and considering the wider availability and competing uses of water in the surrounding area."
