Put Appliances on a Voltage Diet

America’s home appliances need to go on a diet. Utilities across the country are feeding them too much voltage, wasting energy and creating needless greenhouse gas emissions.

Although ordinary AC power outlets are rated at 120 volts, the average U.S. household receives 122.5 volts, according to a recent article in IEEE Spectrum, published by the Institute of Electrical and Electronics Engineers. Utilities are permitted to deliver anywhere from 114 to 126 volts, but tend to run on the high end to avoid any problems with customer equipment under a wide array of operating conditions.

If utilities could drop their average delivered voltage to 118 volts, the power savings would be significant, according to a recent study by the Pacific Northwest National Laboratory (PNNL).

Small compact fluorescent lamps would cut power consumption by 8 percent. 75-watt Incandescent bulbs would save 6 percent, as would fans. Old-fashioned CRT televisions would see a power savings of 4 percent.

On average, the lab reported, reducing voltage on just 40 percent of larger distribution lines nationwide could slash national electricity consumption by 2.5 percent with no degradation of service. That’s huge.

Take California, for example. If peak demand is 50,000 megawatts, a reduction of 2.5 percent would save 1,250 megawatts—the equivalent of two medium-sized power plants.

The PNNL study confirms research performed a decade ago during the California energy crisis by Willard Wattenburg at Lawrence Livermore National Laboratory. In his subsequent report to the California Energy Commission, he stated:

Surprisingly, all modern appliances, air conditioners, and business  equipment tested performed well at voltages  down to 105 volts. The efficiency of all appliances and motors tested was better at 110 volts than at the standard 120 volts that most utilities supply to their customers. Most important of all, the equipment used less energy at lower voltages. . . . Field tests on fully loaded utility distribution lines in Los Angeles showed power reductions of 2% for voltage reduction of 5%, as predicted from the previous laboratory tests.

Unfortunately, lowering average voltages without letting them drop dangerously low for some customers on the end of a distribution line is not a trivial task. Until recently, utilities had no easy way to measure line voltages. Varying customer loads can change voltages quickly and unpredictably—which is why utilities typically play it safe and run high most of the time.

Smart meters and other devices being developed for distribution system automation, along with sophisticated new computer controls, are now making it possible to fine-tune line voltages. Installing them will take time, testing and money. But  “the return on investment for a volt/VAR optimization project is usually less than two years as a result of cost savings from reduced system losses and reduced generation costs,” according to one industry champion.

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