The quest for efficiency improvement raises questions regarding the optimal air temperature for data centers. The ASHRAE TC-9.9 committee has recently adopted an extension of the recommended thermal envelope for server inlet temperature and humidity. A popular hypothesis suggests that total energy demands should diminish as the server inlet temperature increases.

This paper tests that hypothesis through the development of a composite power consumption baseline for a mixture of servers as a function of inlet temperature and applying this data to a variety of cooling architectures. The goal is to find the optimal temperature range where the combined IT and cooling load is minimized. Data presented is based upon actual sealed testing of different cooling systems when subjected to the simulated composite server behavior. The testing revealed a complex interaction between server power and total data center energy consumption in which energy savings is realized within a temperature sweet spot. This temperature sweet spot varies by equipment, containment solution, and other factors.