This article was originally published in the November/December 1993 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online November/December 1993




Leaking Electricity


by Alan Meier

Alan Meier is Executive Editor of Home Energy

In many electrical devices the off switch is a lie. Sometimes appliances leak electricity.

Many appliances leak electricity. That TV, VCR, or stereo (to name just a few items) continues to draw small amounts of electricity even when providing no service and switched off. Some examples of these appliances were described in an earlier article (see What Stays On When You Go Out, HE Jul/Aug '93, p.31), but a Swedish researcher just published much more detailed measurements on the widespread misrepresentation of the humble off switch. This study is particularly useful because it provides data on new equipment.

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


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


A Refresher Course on Energy and Power

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


The trick, however, is to use the correct units for time. The simplest approach is to express all power in the form of kilowatts (that is, in thousands of watts). This is especially convenient, because the rates are typically expressed in cost per kWh. When using kilowatts, the correct time unit is hours. Then the time is simply the number of hours in a month, that is:

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


The 100 W bulb is a 0.1 kW bulb. If it operates constantly for a month, then the energy consumed is:

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


If electricity costs 10 cents/kWh, then that light bulb cost about $7.20 per month to operate. The most common error in the calculation is forgetting to convert the power from Watts to kilowatts, resulting in an answer that is a thousand times too high. (Note that the official designations are W for watts, kW for kilowatts, and kWh for kilowatt-hours.)


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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