Less is more when it comes to beef on the bun (at least according to your doctor), and the same now appears to be true for AC voltage. Research by the Electric Power Research Institute (EPRI), in Palo Alto, Calif., is confirming that many electrical devices work equally well and use less energy at lower voltages, and that offers utilities a big conservation opportunity. By trimming the voltage they deliver, distribution utilities in the United States could slim the nation's power appetite by 3 percent—the equivalent of unplugging every refrigerator in the country—according to an August 2010 analysis from the Department of Energy's Pacific Northwest National Laboratory (PNNL) (PDF).
Some utilities are facing push-back from consumers disenchanted with smart meters and riled by real-time pricing for electricity. So the best news for utilities is that such conservation voltage reduction, or CVR, should cut energy use without asking consumers to change their behavior. CVR can also help stabilize the grid.
CVR operates within the wiggle room offered by electrical standards. The standard for the nominally 120-volt AC power in the United States and Canada, for example, calls for 114 to 126 V. The range is practical, given the ever-shifting power demand on a distribution system. Utilities generally measure and control voltage at their substations and aim for the higher end of the range to avoid browning out customers at the ends of the lines. The result is that, on average, U.S. customers get 122.5-V power.
Until recently, most utilities saw no need to operate differently, assuming that voltage had a negligible effect on power demand. And indeed that assumption is true for some loads. Electric heaters on a lower voltage simply run longer to deliver the same heat, resulting in no savings. But other appliances can get by at lower voltages by doing less work. For example, at the low end of the voltage range, lights dim imperceptibly.
The big-ticket item for CVR appears to be the induction motors in fans, refrigerators, and dozens of other appliances. Motors tend to operate at a lower mechanical load than they are rated to handle. As a result, higher voltages generate stronger magnetic fields than the motors can use, throwing energy away.