This article was originally published in the May/June 1999 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online May/June 1999
Video Networks: A Surprising Energy Drain
by Alan Meier and Karen Rosen
Karen Rosen is a senior research associate at Lawrence Berkeley National Laboratory.
TVs and VCRs are typically dismissed as minor energy consumers in homes. But many homes have three, four, or even five TVs--plus VCRs, cable boxes, and video games. They add up to a big part of a home's total electricity use, especially when standby losses are taken into account.
Although some standby power is used in these devices for features like clocks and remote-control operation, much or most of it is consumed by the appliances' power supplies, which convert alternating current into direct current. However, because of their variety of functions, different appliances use significantly different amounts of power.TVs and VCRs A typical 25- or 27-inch TV uses roughly 90 watts when turned on, about the same amount of power is used by a standard incandescent light bulb. However, there is a wide range--TVs can draw anywhere from 25 to 250 watts, depending on the size of the screen. In our research at Lawrence Berkeley National Laboratory (LBNL), we compiled measurements from 372 TVs. We found that on-mode power consumption for these TVs averaged about 74 watts (see Figure 1). Power consumption values for popular screen sizes are given in Table 1.
Almost all TVs have standby losses (see Figure 2). The standby power maintains the remote control features, which nearly all TVs now have. A small amount of standby power may also be used to maintain memory for channel settings. For TVs that are used less than one hour per day, on average, the standby energy consumption can actually exceed the on-mode energy consumption. In other words, on an average day these TVs use more energy while they are off than they use while they are on.
VCRs consume less power than TVs; they only draw an average of 17 watts while recording or playing back videocassettes. From our research, we found that when VCRs are on, but are not playing or recording, they consume about 13.5 watts. Results from 126 VCR power measurements are shown in Figure 3. When VCRs are plugged in but switched off, they use about 6 watts. This power is used to maintain the remote control, clock display, and memory. Because the power use of the active modes (such as play and record) is only slightly higher than power use of the passive modes (on and off), and because the typical VCR is active less than six hours a week, most of the energy that VCRs use over the period of a year is consumed while they are off rather than on.
According to our results, standby losses account for 23% of total TV energy use, and more than 50% of VCR energy use. What's more, only 5% of VCR energy is used to perform its intended function: to play or record videos (see Figure 3). All in all, we figure that the time TVs and VCRs are not performing their intended functions accounts for nearly 40% of their total annual energy use.Set-Top Boxes Set-top boxes include cable boxes; video games; and various converter boxes, such as satellite decoders and digital converters. The number of set-top boxes in a home doesn't necessarily increase with the number of TVs, because it's possible to use splitters and because some TVs aren't connected to the household's video network. Nevertheless, we expect that the typical home contains at least one set-top box.
According to Nielson Media Research, about 74% of homes in the United States receive their TV signal via cable or satellite. Almost all new TV sets are cable ready, which means that they need no cable box; but some people use the boxes to get special features such as pay-per-view and certain premium channels. According to the Nielsen television survey, at least 40% of homes have boxes in order to receive these features. The cable boxes are typically rented from the cable service provider and are manufactured only by a few large firms.
Until recently, nobody was interested in reducing the energy use of cable boxes, so perhaps it is not surprising that their power consumption is so high. We found units that ranged from 5 to 20 watts. Worse, cable boxes use nearly as much power when they are off as when they are on--in some cases, it appears that switching them off with a remote control does nothing more than switch a light from green to red. The annual energy use of cable boxes ranges from 40 to 175 kWh per year, or about 120 kWh per year for the average model.
Satellite decoders consume even more power. We found that decoders use from 11 to 21 watts while switched on and from 11 to 18 watts while switched off. Assuming the median values of 15 watts for both on and off, satellite decoders use around 130 kWh per year.
Video games are also part of the video network in one-third of U.S. homes. These games typically draw about 1 watt when off and only about 10 watts when on. Since people use video games about 3 hours per week, these use an extra 10 kWh per year in their homes.
The most recent addition to the household video network is the Internet terminal (such as webTV). These devices use 5-21 watts when on, and 4-9 watts when off. Since this is a new technology, there isn't much information on how many hours Internet terminals are used, or whether they replace conventional TV viewing; however, standby losses alone ensure a minimum of 40 kWh per year. The use of Internet terminals--like the use of video games--requires the TV to be switched on, and this is where the kilowatt-hours add up. At one hour per day, one terminal would use an extra 70 kWh per year, including TV use.Wait! That's Not All! More devices are joining the home video network every day. Retailers are calling 1999 the year of the digital versatile disc (better known as the DVD). DVD players now exist in roughly one million homes, and their numbers are growing fast. Like a VCR, a DVD player consumes more energy over its lifetime when it is switched off than when it is switched on. At LBNL, we found that when off, DVD players leak anywhere from 2 to 7 watts. Nonstop consumption at 4 watts adds up to 35 kWh per year.
Stereo and high-quality sound options on video networks are also gaining wider use. These features require another amplifier, either an existing amplifier from a separate audio system, or a new amplifier. Either way, convenience may dictate that the amplifier stay switched on all the time. This can easily add 10 watts--or 90 kWh per year--to the video network's consumption.
The list goes on. Some people find it inconvenient to switch off a TV after leaving the room, so there's a gadget to convert the infrared signal used in the remote control to a radio signal. This permits users to control the TV or stereo through walls and doors. This infrared-to-radio converter draws a constant 1 watt (9 kWh/yr).Busy Eyes of Couch Potatoes On the average day, the occupants of the average U.S. home watch an astounding seven and a half hours of broadcast television, half an hour of videos, and ten minutes of video games. We combined these viewing times with energy use data to estimate annual energy use of TVs and VCRs. To see how much electricity goes to video appliances in a home, refer to Table 2, which lists energy use for typical situations. Clearly, each home will be different, but this is a starting point for trying to figure out where the electricity goes.
A typical home--that is, one equipped with two TVs, one VCR, and a cable box--will consume more than 500 kWh per year. That can easily equal 5% of a typical home's average electricity use (based on 10,000 kWh per year). Energy use is higher in homes with more than one TV and/or VCR because, although overall household TV viewing hours may be the same, the extra TVs and VCRs that are not being watched are still consuming standby power. For example, in a home with five TVs, two VCRs, and two set-top boxes, video electricity consumption probably accounts for 10% of the home's total. This is right up there with refrigerators and other major appliances.Few Energy-Saving Options The best way to save video network standby energy use is cheap but not always convenient--pull the plug. Some people do plug their video appliances into power strips and switch them off and on via the power strip's master switch, but this isn't practical if the residents use the VCR's timer features or its memory of channels.
New equipment is sometimes more efficient, so there may be savings when old units are replaced by new ones in the future. New VCRs, for example, have significantly lower standby losses than old ones. Unfortunately, the efficiency of TVs has barely changed in the last ten years. This means that a new 27-inch TV uses the same amount of power as the ten-year-old unit that it is replacing.
Much progress is being made in the video network industry toward reduction of standby losses. One-watt standby loss is a goal of many manufacturers, and some units are already there or very close. The bad news is that the standby loss is not listed on the product, so it's impossible to directly identify the units with lowest standby losses. However, Energy Star labels make selection easy. The Energy Star levels of standby losses (see Table 3) are higher than 1 watt, but units that comply with Energy Star requirements typically use much less power than the maximum wattage allowed, and standby consumptions are dropping fast. Compare the values in Table 3 with the field measurements in Figures 2 and 3 to get an idea of the savings.
Little can be done to cut the power use of set-top boxes. Manufacturers of these units have made almost no effort to reduce power consumption in either on or off mode (although this may change). It is important for users to make sure that the box is actually needed; sometimes the TV or VCR is cable ready and doesn't need a box.
Unplugging is still an option, although this should be done with care. Some cable service providers issue dire warnings of service interruptions if their set-top boxes are unplugged. Other providers actually advise customers to unplug cable boxes during thunderstorms, and most boxes seem to work quite well after power failures (even when the failure lasts for days). For people who are leaving on a long vacation, unplugging all the TVs, VCRs, and set-top boxes seems like a sensible safety precaution--one that will also save money.
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