Energy Use of U.S. Consumer Electronics
at the End of the 20th Century
Karen Rosen, Lawrence Berkeley National Laboratory
Alan Meier, Lawrence Berkeley National Laboratory
The
major consumer electronics in U.S. homes accounted for over 10% of U.S.
residential electricity consumption in 1999, which is comparable to the
electricity consumed by refrigerators or lighting. We attribute 3.6% to video
products, 3.3% to home office equipment, and 1.8% to audio products.
Televisions use more energy than any other single product category, but
computer energy use now ranks second and is likely to continue growing. In all,
consumer electronics consumed 110 TWh in the U.S. in 1999, over 60% of which
was consumed while the products were not in use.
Until recently, energy analysts have dismissed the electricity use of consumer electronics as an insignificant portion of U.S. residential energy use (Meier et al. 1992). This view has changed as the stock of these products increased, and as research revealed higher than expected energy consumption levels for many of these devices. Recent U.S. research has focused on the electricity use of specific consumer electronics products (Rosen & Meier 1999a; Rosen & Meier 1999b; Rosen et al. 2000). Studies in Europe (Siderius 1995; Meyer & Schaltegger AG 1999; Sidler 2000), Australia (Harrington 2000), New Zealand (EECA 1999) and Japan (Nakagami et al. 1997) have produced similar results. To date, however, there have been no comprehensive estimates for the energy use of the entire category of consumer home electronics – that is, video, audio, telephone, and computer-related products.
We report here a preliminary estimate of total electricity consumption for the U.S. consumer electronics end use in 1999. Products included in this study are listed in Table 1.
Table 1. Consumer Electronic Products Included in this Study
|
Video |
Audio |
Set-top Boxes |
Telephony |
Office |
|
Analog
TV Digital
TV VCR DVD
player |
Component
stereo Compact
stereo Portable
stereo Clock
radio |
Analog
cable Digital
cable Digital
satellite Game
console |
Answering
Device Cordless
phone Cordless/Ans.
Dev. Cell
phone charger |
Computer Printer Fax/Copier Peripherals |
NOTES: TV = television; VCR = videocassette recorder; DVD = digital versatile disc. ‘Analog TV’ includes TV/VCR combos. ‘Computer’ includes monitors.
The ideal approach to estimating energy use would employ a long-term appliance-monitoring program involving a statistically representative group of homes. Findings of this program could then be extrapolated to the whole country. Studies in France (Sidler 2000) and New Zealand (EECA 1999) have used this approach; however, this approach is both expensive and time consuming. Instead, we resorted to a bottom-up approach combining direct measurements of individual devices and survey data. The approach consists of four major steps for each device:
1. Determine the principal operating modes
2. Estimate the time spent in each mode
3. Measure the power use of actual products in each mode
4. Estimate the number of units of that product in U.S. homes
These steps are briefly described below. Details of the methodology can be found elsewhere (Rosen & Meier 1999a; Rosen & Meier 1999b; Rosen et al. 2000).
Many consumer electronics operate in different modes (or states) during normal usage. Typical TVs have just two modes, but an audio or computer system may have a dozen. An accurate estimate of energy consumption requires an estimate of the energy use for each mode. This entails identifying common modes, then estimating average power levels and usage for each.
This study covers a wide variety of product types, so we adopted a much cruder classification of modes than would be appropriate for a single appliance. This simple classification is consistent with the quality of the other data used in this study. The operating modes assumed for this report are listed in Table 2.
Table 2. Common Consumer Electronic Modes
|
Mode |
Description |
|
Active |
The unit is performing a requested service, e.g. record, play, talk,
etc. |
|
Charge |
The battery charger provides current to the battery |
|
Idle |
The unit is on but not Active. This includes computer Sleep modes. |
|
Standby |
The unit is plugged in and appears off to the user |
|
Disconnected |
The unit is unplugged |
Note
that Idle may occur (1) after the user switches the unit on but before requesting
a service, or (2) after the service ends (e.g. end of tape or automatic “Sleep”
modes) but before the user switches the unit off. Some consumers never switch
off units with idle modes.
Of the three types of data needed for a bottom-up estimate of energy consumption, the usage profile is usually the most difficult to acquire. Conventional surveys are not helpful in estimating usage patterns for the Standby and Idle modes, which are critical for accurate estimates of unit energy use. Office equipment is particularly complicated because there are so many Standby and Idle modes and such a great range in the power consumption of the different modes.
Estimating usage patterns for this investigation involved a variety of data sources and usage assumptions that varied from product to product. In general, Active usage values were based on consumer surveys, while the remaining values were estimated from anecdotal data or best guesses.
We compiled
measurements of appliance power consumption from many sources, including
stores, homes, and repair shops. Most measurements were performed by LBNL staff
using the following procedure:
1. Identify the operational modes to measure
2. Plug the power cord of the unit into the power meter
3. Record the Standby power draw before switching the unit on
4. Record the power draw, in watts, of the unit in all other modes studied
5. Switch the unit off, and confirm the Standby mode power consumption
We used a true RMS wattmeter that was custom-built for measuring
low power levels with high resolution (0.1W) and accuracy (±0.5%+0.1W). This meter
displays average power every second. Where readings fluctuated, we visually
estimated the average power draw based on the readings. Readings typically
fluctuate only one or two tenths of a watt.
We employed two methods in estimating the number of units in U.S. stock; one used ownership surveys and the other recent sales data. In most cases, the two methods resulted in similar stock estimates. Where results differed significantly, we chose the estimate that seemed more probable.
To calculate the average unit energy consumption (UEC) for each product type, we weighted the arithmetic mean of the measured power levels to reflect the average usage profile, and then multiplied by the number of hours per year. National energy consumption values were calculated as the product of UEC and the number of units nationwide.
Using the methods described in the previous section, we collected over one thousand product measurements. Table 3 shows the average measured power levels in watts (W), estimated usage patterns, and average annual UEC values.
Table 3. Usage, Power, and Unit Energy Consumption of Consumer Electronics
Product
|
Units Measured
|
Standby |
Idle |
Charge |
Active |
UEC |
||||
|
|
|
W |
Time |
W |
Time |
W |
Time |
W |
Time |
kWh/yr |
Analog
TV
|
372
|
4.6 |
84% |
|
|
|
|
75 |
16% |
140 |
|
Digital
TV |
14 |
8.8 |
84% |
|
|
|
|
177 |
16% |
320 |
|
VCR |
126 |
5.9 |
77% |
13 |
24% |
|
|
17 |
4% |
74 |
|
DVD |
18 |
4.1 |
72% |
15 |
24% |
|
|
17 |
4% |
64 |
|
Component
Stereo |
119b |
3.0 |
65% |
43 |
16% |
|
|
44 |
19% |
150 |
|
Compact
Stereo |
19 |
9.8 |
72% |
20 |
18% |
|
|
22 |
10% |
110 |
|
Portable
Stereo |
22 |
1.8 |
51% |
4.9 |
13% |
|
|
6.1 |
6% |
17 |
|
Clock
Radio |
33 |
1.7 |
99% |
|
|
|
|
2.0 |
2% |
15 |
|
Analog
Cable Box |
42 |
11 |
78% |
|
|
|
|
12 |
22% |
95 |
|
Digital
Cable Box |
5 |
23 |
78% |
|
|
|
|
23 |
22% |
200 |
|
Satellite
Receiver |
31 |
16 |
78% |
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