The Overlooked Variable in Data Center Water Efficiency: Cooling Tower Cycles of Concentration

Water is moving from a design consideration to a permitting and community issue for data centers as rack densities rise beyond 50 kW and AI training increases thermal load. While overall water-use scale for hyperscalers is increasingly documented—estimated at roughly 1.14 to 1.70 million litres per day per facility—the under-discussed lever is “cycles of concentration” in evaporative cooling towers. DOE figures cited say many towers run at two to four cycles; increasing from three to six can cut makeup water by about 20% and blowdown by around 50%. Because evaporation is thermodynamically set by heat load, blowdown becomes the controllable treatment variable.