Free cooling is a mainstream energy-saving concept in data center cooling design, used to reduce chiller compressor runtime by leveraging low outdoor temperatures (air-side) or low cooling-water temperatures (water-side) during suitable seasons. Therefore, describing the technology as “not mature enough and should be used with caution” is the false statement when discussing its advantages. In practice, free cooling has broad industry adoption and is considered a proven approach when applied with correct engineering, such as proper filtration, anti-condensation control, heat exchanger selection, and automatic control strategies. Its advantage is that it can directly utilize the outdoor “cold source” to remove heat, which significantly reduces cooling power consumption compared with full mechanical refrigeration, improving overall energy efficiency and supporting lower PUE targets. It also makes full use of seasonal and day-night temperature differences: the system dynamically switches among free cooling, partial free cooling, and mechanical cooling to balance reliability and efficiency. The key point is maturity: the benefit of free cooling comes from well-established principles and widely implemented architectures, not experimental technology.