Data centers are significant energy users and require continuous cooling to maintain high levels of computing performance. The majority of data centers have direct-expansion cooling, which typically accounts for approximately 50% of the energy usage of data centers. However, using typical meteorological year 3 (TMY3) weather data and a simple psychrometric bin analysis, alternative cooling strategies using a combination of economizer, evaporative, and supplemental direct expansion (DX) cooling have been shown to be applicable in all climate zones in the United States. Average data center cooling energy savings across the U.S. was approximately 80%. An analysis of cooling energy savings is presented for various ASHRAE climate zones. The psychrometric bin analysis is conducted for the ASHRAE recommended and allowable operating environment zones as well as a modified allowable operating environment. Control strategies are discussed. Finally, examples of energy-efficient data centers using alternative cooling strategies are presented.