Video Networks: A Surprising Energy Drain

Karen Rosen is a senior research associate at Lawrence Berkeley National Laboratory.

Figure 1. Actual power measurements of TVs while switched on.

Table 1. Power Use of TVs by Screen Size Average Power Screen Size (Inches) Units Tested Off On Percent of U.S. Homes2 18 or less 38 3.1 watts 47 watts 25% 19-20 97 5.1 watts 68 watts 36% 25-27 145 4.9 watts 90 watts 31% 30-36 54 5.3 watts 114 watts 5.6% 39 or above1 32 3.5 watts 142 watts 2.4% Weighted average  4.5 watts 74 watts 1This category includes projection TVs. 2This is the percent of U.S. homes that have a TV of this size.

How Many TVs Are There, Anyway? In 1997, the average house had 2.1 TVs and 1.3 VCRs. But averages can be deceptive: roughly 30% of U.S. homes-that's 30 million-have 3 or more TVs, and about 3% of U.S. homes have 5 or more. VCRs are less common, yet more than 30% of U.S. homes have two or more VCRs. Combined TV/VCRs are becoming increasingly popular, but as of 1997 they were found in fewer than 10% of U.S. homes. About 74% of homes get TV via cable or satellite, and about 40% have cable boxes or satellite decoders. Finally, about a third of U.S. homes have video games (such as Nintendo, Sega, or the Sony Playstation). Less than 1% have Internet terminals in their video systems. Currently, nearly all TVs in U.S. stock are color models and have remote controls. Older, less efficient, black-and-white TVs are rapidly vanishing (indeed, there are so few around that they are not counted in surveys).

Figure 2. Actual power measurements of TVs while switched off: two-thirds use more than 3W.

Percentage of Energy Used by TVs and VCRs in Different Modes

Figure 3. Both TVs and VCRs have high off-mode energy use. For VCRs, only 5% of the total energy use occurs when the machine is operating for its intended purpose, recording or playing video cassettes.

Table 2. Estimated Electricity Use of Home Video Networks Situation kWh/Year Single TV only 260 TV + VCR 330 Typical house (2 TVs + VCR) 380 2 TVs + VCR + cable box 500 3 TVs + 2 VCRs + cable box + video game 610 Couch potato's paradise (5 TVs + 3 VCRs + 2 cable boxes + 2 video games + 1 Internet terminal) 940

Table 3. Standby Power Limits for Energy Star and Actual Levels of Complying Units Energy Star Level Average of Complying Units in Late 1998 TVs 3 watts 1.7 watts VCRs 4 watts 3.0 watts TV/VCR combos 6 watts 4.7 watts

Figure 4. Actual power measurements of VCRs while switched off. More than 50% of a VCR's energy consumption occurs in this mode.

Figure 5. Actual power measurements of VCRs while switched on.

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

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

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!

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

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

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.
 
 
 

Home Energy can be reached at: contact@homeenergy.org
Home Energy magazine -- Please read our Copyright Notice