"INTODUCTION As projections for IT equipment heat densities continue to rise@ there is renewed interest in finding solutions to minimize data center electrical requirements. Energy benchmarking in data centers is very useful for understanding the operation and energy requirement for the center as whole and for individual systems and components that make up the center. High-level information obtained throught benchmarking can be helpful in many ways@ such as ensuring adequate infrastructure and reliability@ planning for future growth@ projecting utility costs@ and negotiating utility contrats. Then@ by ""peeling the onion"" and examining the end uses within the data center@ additional information on the individual systyem's energy performance is revealed. And finally@ through examination within the system's@ the energy performance of key components can be evaluated. By comparing energy performance at the end-use level@ an interesiting picture emerges. All systems and components are not created equal. Large variation in energy use and relative efficiency is evident when infrastructure systems and components are compared to comparable systems in other data centers. Similarly@ energy efficiency of the IT equipment itself varies considerably while performing similar computing work. Byexamining the better-performing systems and components@ certain designs and operating strategies@ or ""best practices@"" that lead to more energy-efficient operation become evident. A review of over 22 data centers' energy performance helped to identify over a dozen best practices. This paper discusses five of these that contributed to better overall energy efficiency in the data centers that were studied."