Berkeley Lab Research News


Homes That "Leak" Electricity, And How To Plug Them

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By Allan Chen,

May 20, 1997

BERKELEY, CA -- As electrical appliances in homes become more specialized or provide new services once unavailable to the general public, they are using a growing amount of energy, even when switched off or not providing the service for which they were designed, says a scientist at Ernest Orlando Lawrence Berkeley National Laboratory.

"Many household appliances draw power in their 'standby' mode," says Alan Meier, a scientist in the Energy Analysis Program of Berkeley Lab's Environmental Energy Technologies Division. "These include common household appliances such as televisions, cable boxes, VCRs, answering machines, alarms, smoke detectors, cordless phones, fax machines, video games, even rechargeable electric toothbrushes."

Energy specialists call this "leaking electricity" because the devices are using energy without performing their principal function.

Meier and colleagues Steve Greenberg of Berkeley Lab, and Leo Rainer of the Davis Energy Group estimate that the national power consumption lost to leaking electricity is 5 gigawatts (billion watts), or the equivalent of five standard power plants, and growing. They have also developed strategies to reduce this loss, including a circuit which reduces the power draw of appliances that need continuous energizing.

To determine how much electricity residences are leaking on average, Meier worked with several colleagues to measure the actual leakage of homes in California, Florida and Japan. Hidetoshi Nakagami of Japan's Jyukankyo Research Institute monitored electricity use in four Japanese houses, Danny Parker of the Florida Solar Energy Center studied a home in that state retrofitted for energy-efficiency, and Rainer studied six California homes, three new, and three with energy-efficient retrofits.

"Based on these measurements, and the saturations of the principal electricity-leaking appliances in American homes, we estimate that the average home leaks about 50 Watts, or 450 kilowatt-hours per year," explains Meier. "Since the average residential energy consumption in the U.S. is nearly 10,000 kilowatt-hours per year, this is about five percent of a home's electricity use -- roughly two-thirds the consumption of a new refrigerator."

The U.S. houses in the study drew anywhere from five to 23 percent of the houses' total power consumption, while the Japanese houses drew between 10 and 17 percent. The fraction of leaking electricity in U.S. and Japanese homes is similar because the U.S. houses in the study were more energy-efficient than the average U.S. house. Japanese homes use less electricity than U.S. homes, according to Meier.

"Newer models of some appliances," says Meier, "will leak less electricity in the future. Televisions, for example, currently draw about 40 Watts to maintain their remote control and instant-on features, but new models on the drawing board will draw five to 20 Watts. Computer, monitors, fax machines and some other appliances are also getting more efficient, thanks to the Environmental Protection Agency's Energy Star voluntary guidelines."

But Meier says that other trends, like the growth in certain appliances and changes to building codes, are increasing electricity leakage. "The saturation in American homes of emerging electronic appliances like burglar alarms, garage door openers, telephone answering machines, cordless phones and others is increasing," he says.

Stricter building codes require developers to install ground fault circuit interrupter-protected outlets. Older codes mandated these only in bathrooms to reduce the danger of electrical shock. Now, kitchens and other special rooms must have them too. Codes also now demand the hard-wiring of three or four smoke alarms into the home's electrical system: in the bedrooms, hallway and garage.

Reducing or eliminating leaking electricity would have a number of other benefits besides saving energy, which of course reduces the environmental impacts of energy generation.

"It would remove a potential fire hazard or a danger of shock--when the appliance is 'off,' it is truly off," says Meier. Leaking electricity also generates heat, which increases a home's air conditioning load. And, the "leaked" electricity has a poor power factor, meaning that it can degrade the performance of sophisticated electronic equipment such as the home personal computer.

Meier and his colleagues have been studying ways to reduce these leaks and have found some technical options. The low voltage power supply (the little black box that plugs into the wall outlet) is the culprit in some appliances. Cheaper models have high power losses, up to three Watts each. Higher quality, Underwriters Laboratory-certified power supplies already exist that have a three-way on-ready-off switch on the side. In the off position, an appliance equipped with one of these is truly turned off.

Existing photovoltaic technology provides another solution for consumers with certain battery-based appliances like portable computers or cordless telephones. Solar PV-charge kits can take the place of the household outlet for keeping some batteries charged.

To address the power draw of appliances that need continuous energizing such as TVs and VCRs, Meier, Greenberg and Rainer have designed a circuit that draws power only when a small battery mounted in the appliance needs power. The rest of the time, the circuit switches itself off. Manufacturers could design these circuits into their appliances, as well as by improving the quality of the power supplies they use.

This work has been published in the Proceedings of the ACEEE Summer Study on Energy Efficiency in Buildings; earlier related papers appear in Home Energy and Energy--The International Journal.

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