High-Efficiency Power Supplies

As with processors, many of the server power supplies in use today are operating at efficiencies below what is currently available. In 2005, the U.S. EPA estimated the average efficiency of installed server power supplies at 72 percent. Currently, best-in-class power supplies are available that deliver efficiency of 90 percent. Use of these power supplies can reduce power draw in data center by 124 kW — or 11 percent of the 1127 kW total.  As with other data center systems, server power supply efficiency varies depending on load. Some power supplies perform better at partial loads than others, and this is particularly important in dual-corded devices where power supply utilization can average less than 30 percent.  Sizing power supplies closer to the actual load presents another opportunity to decrease power use. Maximum configuration is about 80 percent of nameplate rating and the typical configuration is 67 percent of nameplate rating. Server manufacturers should allow purchasers to choose power supplies sized for a typical or maximum configuration.