Alan Meier is Executive Editor of Home Energy

Eje Sandberg visited several electronics stores in Sweden. He measured the power consumption of over a hundred TVs, VCRs, and other domestic electronic equipment when switched "on" and "off." The results are shown in the figures.

Sandberg concentrated on TVs, VCRs, and some audio equipment because he wanted to measure the range in "off" electricity consumption. While these measurements were made in Sweden, the international nature of the electronics industry means that similar values would be found for TVs and other appliances in the United States. Figure 1 shows the range of electricity consumption for four appliances. All but four devices tested drew power when switched "off". Sandberg found these results so surprising that he called it "leaking electricity." TVs and VCRs had the highest power at "off"--many topped 10 Watts or 7 kWh/month. CD players were much less: 2-5 Watts.

What is this power used for? There are several applications. TVs must keep some circuits energized in order to provide "instant on" and to receive transmissions from the remote control. The penalty used to be much higher in old tube TVs, however, the new, solid-state models are much more efficient. Other features in TVs or VCRs requiring power are clocks and digital displays. And the transformers for low-voltage halogen lights draw power even when the lights are switched off.

Although 10 W is a tiny amount of power (less than $1/month), there are several reasons why the leaking electricity deserves attention. First, most homes have several of these appliances and they easily add up to $10/month. Second, energized appliances represent a small but significant fire and shock hazard. Switched-off appliances have been blamed for starting some home fires. Finally, leaking electricity is a serious matter for those people on the electrical frontier, relying on photovoltaic collectors for their electricity supplies. Leaking electricity can drain storage batteries without warning.

Sandberg measured the power consumption of other appliances, including a parabolic receiver and a telephone answering machine. The mean power draws for those appliances (when turned off) are shown in Figure 2. Sandberg's results are supplemented by measurements made by Pam Coxson in San Francisco. (These items are marked with a "USA" after them.)

Plugging the Leaks

Sandberg has three recommendations regarding leaking electricity. While these recommendations were proposed for Europe, they are just as relevant in the United States. First, he proposes that all manufacturers declare their "no load" losses, the power draw while switched off. (Presumably this would appear on the appliance's nameplate.) Sandberg doubts if many consumers will change their purchasing habits as a result of this new information, but they encourage manufacturers to avoid the embarrassment of the declaration by redesigning their equipment.

Second, Sandberg proposes that manufacturers be required to establish a "true off" position. In many cases, this would mean that a 3-position switch would replace the current 2-position switch. Again, most consumers would probably use the "partial off" position, but at least they would realize that the television or dustbuster was still drawing power.

Alternatively, a standard could be established to limit the amount of no-load losses. For example, it might require low-voltage transformers to draw less than 2 W during no-load mode. This might be more complicated to establish (especially because most European countries lack any energy efficiency standards).

Unplugging appliances is the simplest way to minimize consumption, though it is not always possible, or at least not convenient. For the present, however, it is important to recognize that leaking electricity is responsible for part of the utility bill. n

Note

Sandberg's findings were published in "Proceedings of the 1993 ECEEE (European Council for an Energy Efficient Economy) Summer Study," held in Rungstedgard, Denmark.

When an appliance draws 100 watts, what is its monthly energy cost? This is a simple calculation but it requires a clear understanding of the difference between energy and power. Electrical power is the flow of electricity (like gallons/minute of water), but the monthly bill is an amount of electricity (like total gallons) usually expressed as kilowatt-hours. To convert the flow to an amount of energy (such as kilowatt hours), one must multiply by the time, that is, one month.

energy = power X time

hours in a month = 30 days/month x 24 hours/day = 720 hours

monthly use = 0.1 kW 2 720 hr/month = 72 kWh/month

Figure 1. Measurements of power demand for four kinds of appliances while switched "off."Source: Eje Sandberg

Figure 2. Measurements of power demand for other appliances while switched "off."Source: Eje Sandberg and Pam Coxson

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