# DX vs Chilled Water Crossover Direct expansion (DX) cooling uses **dedicated condensers per rack pair with refrigerant lines** running directly to the cooling units. Chilled water uses a central chiller plant that distributes cold water through pipes to air handlers or in-row coolers. The crossover point is roughly **~1MW of IT load**. Below 1MW, DX wins on cost. Each rack pair gets its own condenser — simple, self-contained, no central plant. The main cost variable is **condenser cable length:** short runs cost ~$400 each, long runs (when condensers are placed far from the MDC) cost ~$2K each. With 24 cables needed for a 400kW deployment, the total cable cost delta is ~$40K. Chilled water adds **€200-300K** for the central plant, pumps, and piping infrastructure. That's 5-7x the cable cost penalty of DX with long runs. Above ~1MW, chilled water becomes more efficient because a single large chiller plant serves many racks more efficiently than dozens of individual condensers. The capital cost of the central plant amortises across more IT load. **Decision rule:** If your total IT load stays below 1MW, DX is the right architecture. If you're planning to scale past 1MW, design for chilled water from the start — retrofitting is painful and expensive. --- See also: [[Cooling and Energy Efficiency Technologies]] | [[Data Center MoC]] | [[Modular Data Centers MoC]]