The energy-saving potential of free cooling in chilled-water systems was investigated. As a preliminary study, simulation was used to quantify the performance of free cooling in a given reference system. To reduce the computational effort for the simulation of long time periods, simplified models for dry and evaporative cooling were developed. The simulation results indicate that free cooling reduces the electric energy demand for cold supply almost by half. In a follow-up investigation, free cooling was implemented in the reference system. The actual energy savings showed good agreement with the simulation forecasts and confirmed the feasibility of the concept.