Efficiency Standards for AC Adapters

phantom load effect of external power supplies (also called adapters, chargers, transformers, and wall warts) is well known. As long as they’re plugged into wall outlets, those little voltage- and current-converting boxes on the power cords of small appliances—ranging from computer printers and cordless tools to baby monitors and electric shavers—continue to use a trickle of electricity, even when the appliance is fully charged or disconnected from them. It’s easy to shrug off those small loads; however, an estimated 1.5

billion external power supplies are being used in the U.S.—at a couple of watts per idle adaptor, there’s a tremendous amount of power in those numbers. Further, the average working efficiency of these transformers is between 30% and 60%. One-third to more than one-half of the electricity is wasted. This is particularly so at part-loads, which account for the majority of operating time. U.S. Environmental Protection Agency (EPA) research estimates that about 6% of all electricity used in the U.S. flows through these power supplies—that’s 207 billion kilowatt-hours (kWh) a year. The average nuclear power plant in the U.S. produces less than 7.5 billion kWh a year.