This article was originally published in the July/August 1996 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.


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Home Energy Magazine Online July/August 1996


Off is a Three-Letter Word

by Michael Lamb

The term off can be a relative one. Over the past few years, there have been several scientific studies showing power is used by appliances that are turned off. I decided to test some of the common appliances found in residences for myself.

To accomplish my mission, I constructed a testing device to meter energy demand (see Making a Phantom Meter). With this device, I started my energy crusade. Table 1 shows the appliances I metered while they were off, their projected yearly energy use, and an estimated yearly cost of energy, assuming that the appliances are plugged in but never used. Any usage would obviously make the costs higher. I have not attempted to compensate the values on the list for power factor, so these results are not exact. They do, however, provide a ballpark range for the devices I tested.

Clearly, no single one of these loads will break the household piggy bank. However, if we consider that there are hundreds of millions of most of these devices around, the size and number of power plants needed to produce the power to do essentially nothing is staggering.

Take televisions, for example. My 27-inch TV has a phantom load of about 13 W. I actually do watch the TV some of the 24 hours per day that it is plugged in. So--departing from Table 1--let's subtract out some of the day as legitimate usefulness. Assuming that the TV is used 3 hours per day, six days per week (I don't watch TV on Saturdays), that's still 150 hours per week (21 x 6 + 24) that the TV sits doing absolutely nothing. Multiply the 13W phantom load by 150 hours per week by 52 weeks per year, and the result is about 100 kWh per year of off-time usage. At an electric rate of 8.5¢ per kWh, it costs me about $8.50 per year.

Not a great deal of money, admittedly. But let's assume that there are 10 million TVs similar to mine in the United States (according to the Energy Information Administration, 94 million U.S. households have TVs and 55 million of those have two or more.) At 100 kWh per year each, this adds up to about 1 billion kWh per year of wasted energy. This is about the same as the yearly usage of 167,000 all-electric houses (at 500 kWh per month per house). At 8.5¢ per kWh, that's about $85 million per year nationwide.

So why do TVs do this? My particular TV uses this energy to maintain its feeble memory of stations I don't wish to watch and to keep the receiver for the remote control ready to respond to my being a couch potato. In some older TVs, power is also used to keep the picture tube filaments warm for faster start-up.

Table 1. Phantom Electrical Loads

One way to save this energy is to kill the power by means of a wall switch or by plugging the appliance into a power strip. Better still, the units could be manufactured so that the hot side of the power cord enters a real switch before it goes anywhere else in the unit. Of course, these solutions will cause the TV to forget which are the undesired stations and not respond to the commanding potato on the couch. To keep this from happening, a good electronics technician can add a battery backup with sufficient capacity to keep the memory intact for those totally off times. The battery can easily last at least several days per charge. Most video cassette recorders already have a battery back-up that lasts 20 minutes or so. Adding a bigger battery would not be difficult.

Another particularly vexing finding was that even the Energy Star computers I metered (both Dell and Gateway models) use a couple of watts even when they're off. This waste can again be avoided by killing the power via a wall switch, or the switch on the power strip or surge protector that most PC users already have. But there is really no reason why the units couldn't be manufactured so that the hot side of the power cord enters a real switch before it goes anywhere else in the computer or monitor.

Turning Off the Phantom

The loads discussed here are small, but they are an example of energy use that is truly wasted. Most people don't even know that they exist. Once they become aware of them, they can take action to prevent electricity from leaking into appliances in their homes.

Michael Lamb is an energy consultant in northern Virginia and is on the staff of the Energy Efficiency and Renewable Energy Clearinghouse.


Other Phantom Research
McCray, Mark Finding and Managing Phantom Parasitic Inverter Loads Parts 1 and 2, Solar Today (July/Aug 1995, Sept/Oct 1995).

Meier, A. Leaking Electricity. Home Energy, Vol 10 No. 6 (November/ December 1993): 33-34.

Meier, A. What Stays on When You Go Out. Home Energy, Vol. 10, No. 4 (July/August 1993): 31-35.

Meier, A., et al. The Miscellaneous Electrical Energy Use in Homes. Energy: The International Journal Vol. 17, No. 5 (1992): 509-518.

Nakagami, et al. (1996). Lifestyle and Energy Tokyo: Jyukankyo Research Institute.

Nore, D. and M. Roberts. Miscellaneous Residential Electrical End Uses: US Historical Growth and Regional Differences. ACEEE Summer Study on Energy Efficiency in Buildings, Vol. 7 (1994): 179-188.

Perez, R. Phantom Loads. Home Power 37 (October/November 1993): 46-48.

Sandberg, E. Electronic Home Equipment: Leaking Electricity. The Energy Efficiency Challenge for Europe 1 (1993): 373-375, published by the European Council for an Energy Efficient Economy.


Making a Phantom Meter

I began by constructing a simple shunt tester out of a 1,000 ohm, 10%, 7-watt resistor, duplex receptacle, and a few other electrical parts. I was concerned about two inherent inaccuracies of my testing system: the tolerance of the 1,000 ohm resistor and the accuracy of the digital multimeter. So I cross-checked my meter with other newer meters at an electronics store and found that mine was pretty close.

I then checked the tolerance of the resistor in a more primitive way. I measured the resistor at room temperature (990 ohms) and then pumped about 14 watts (twice its rating) through it for 60 seconds. This caused the resistor to heat up and change value some. I then quickly measured its resistance again before it had a chance to cool off (1004 ohms). This simple test proved two things to me--I had a pretty good resistor (it changed less than 1.5% under abusive conditions); and when I am testing appliances that are off I should be well within the temperature tolerances of the resistor.

The results achieved from the meter do not account for power factor, which means that it could overestimate actual wattage somewhat. However, the device is an inexpensive way to get a rough idea of the phantom power draw of different appliances. For detailed construction plans, send $1 and an SASE to Michael Lamb, 7920 Appomattox Ave., Manassus, VA 22111. 

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