When you climb into bed at night, ready to shut down for the day, are your home’s electrical appliances doing the same? Some of your appliances do useful work while you sleep—refrigerators and centralized heating systems cycle on and off to keep your food cool and your house warm. Other appliances, like TVs, computers, and modems, are likely also using energy while you sleep, but not performing any useful service. These useless energy draws are referred to as phantom loads, and unless you keep them in check, they will haunt your home’s energy use all night, every night.
The energy wasted by phantom loads is commonly referred to as standby loss. And while a given appliance’s standby loss may be small in terms of power (watts; W), these phantom loads are consuming electricity 24 hours a day, seven days a week. As a result, the cumulative energy (watt-hours; WH) they waste is substantial.
Some quick math can help put phantom loads in perspective in terms of overall energy use. The average U.S. household has about 40 to 60 W of continuous phantom loads running, day in and day out. On average, this amounts to approximately 1,200 WH per day (50 W x 24 hrs./day = 1,200 WH/day) or 1.2 kilowatt-hours (KWH) per day. The same average U.S. home uses about 900 KWH of electricity per month, and 36 KWH per month, or about 4 percent of total electricity use, is due to standby losses. Multiply this figure by 122 million U.S. housing units, and enough energy is wasted by standby losses in the United States to run all of the homes on the continent of Australia, and then some. These figures are the stuff that energy nightmares are made of.
Many, if not most, electronic devices can be phantom loads—TVs; microwave ovens; VCR, CD and DVD players; computers; etc. Products that have external power supplies (wall cubes) are often accompanied by constant standby consumption. The table surveys some phantom loads present in a typical U.S. household. Keep in mind that a home’s standby energy consumption can vary widely depending on the number of appliances and how they are designed.
Phantom loads fall into two general categories—appliances that consume energy even when they’re turned “off,” and appliances that, compared to when they’re fully operational, use a lesser amount of energy to keep displays, remote controls, and power supplies ready for the product’s primary use. Let’s look at the energy use of a DVD player as an example.
One current model DVD player draws 11 W while showing your favorite flick. With no movie playing, and just the LCD display lit, it consumes a little bit less—9 W. But even when you turn off the DVD player, it still draws 3 W. If you look at the DVD player’s energy use modes (playing, on, and off) over the course of a day, some interesting energy use figures come to light.
Let’s assume that you’re a full-on video-head and watch a two-hour movie every night. If you break down the DVD player’s 24-hour energy use by the time spent in each mode, it consumes 22 WH (11 W x 2 hrs.) while the movie’s spinning. If you shut the player off after you’re done watching, the DVD player will still consume another 66 WH (3 W x 22 hrs.) before you plunk down to watch another movie the next night. If you zonk out during the movie and forget to turn the DVD player off, it will consume 198 WH (9 W x 22 hours) over the same time frame. So over a 24-hour period, the DVD player uses three times as much energy when it’s off as when it’s playing, and nine times the energy if you forget to turn it off altogether.
Nearly all of the electronic appliances around your home rely on power supplies to convert the 120 volts AC provided at your electrical outlet to lower-voltage DC to power the appliance’s electronics. The familiar wall cubes you plug in to power your cordless phone or to charge your cell phone battery are both examples of external power supplies.