Summary
- AWS says an in-row heat exchanger design can cut water use by 9% against evaporative air-cooled facilities.
- Amazon reported global data centre water use of 0.12 litres per kWh in 2025.
- The story connects cooling design, AI density, water stress, and European planning scrutiny.
AWS says an in-row heat exchanger design can reduce water use by 9% compared with evaporative air-cooled data centre designs, adding another cooling option to the hyperscale water debate.
The update sits alongside Amazon’s wider 2025 water reporting, which puts global data centre water use at 0.12 litres per kWh. Amazon says its data centres are more than seven times more water-efficient than the industry average and that it is 75% of the way towards its goal of being water positive by 2030.
Amazon’s official water-efficiency briefing says the company uses air cooling for most of the year and water only during hotter periods. It also says reclaimed water is being used across more data centres and that 130 data centres are contracted to use reclaimed water.
Cooling choices are becoming planning choices
The technical distinction matters. Data centres can reduce water use by relying more heavily on air cooling or mechanical cooling, but that can increase electricity demand, particularly during hot periods when power grids are already under stress. Evaporative cooling can reduce electricity consumption but uses water. Liquid cooling can improve heat removal at high rack densities, but it requires more complex design, different plant, and new operational practices.
European developers are now being forced to explain those trade-offs earlier. Planning authorities, local communities, and regulators are increasingly asking how much water a facility will use, whether water is potable or reclaimed, what happens during heatwaves, and whether cooling plant will increase peak electricity demand. The answer cannot be a single efficiency metric. It depends on climate, workload, chip density, grid carbon intensity, water stress, and site design.
AWS’ in-row heat exchanger claim is therefore best read as part of a broader design shift rather than a single product story. AI workloads are pushing heat loads closer to the rack and the chip, while data centre operators are trying to avoid both water-intensive cooling and power-hungry mechanical systems where possible.
Water accounting faces a harder audience
Amazon’s 0.12 litres per kWh figure gives the company a strong efficiency number, but European scrutiny is becoming more local. A global WUE figure does not tell a community whether a specific facility will draw water from a stressed catchment, use reclaimed water, or require new utility infrastructure. Nor does it show whether heat rejection will affect nearby areas during hotter summers.
That is why the next stage of data centre water reporting is likely to be more granular. Operators will be under pressure to publish regional water withdrawal, source type, replenishment projects, cooling approach, and climate-adjusted operating assumptions. EU reporting requirements and national planning systems will push the sector away from broad sustainability claims and towards site-level evidence.
The AWS update still matters because hyperscale design choices often move supplier markets. If in-row heat exchange, liquid cooling, warmer operating envelopes, smart metering, and reclaimed water contracts become standard parts of large cloud builds, MEP contractors and consulting engineers will have to design around them. That affects plant space, maintenance, commissioning, resilience testing, and the relationship between IT and facilities teams.
Cooling is no longer a back-of-house issue. For AI data centres, it is part of the public case for whether a site can be built, powered, and operated without creating unacceptable water or grid pressure.
