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Standby power use in Chinese homes
Energy and Buildings 36 (2004) 1211–1216
Standby power use in Chinese homes Alan Meier a,∗ , Jiang Lin a , Jiang Liu b , Tienan Li c a
Lawrence Berkeley National Laboratory, University of California, Energy Analysis Department, Laboratory, Building 90, Room 2000, Berkeley, CA 94720, USA b CEPREI, Guangzhou, China c CECP, Beijing, China Received 28 April 2003; accepted 31 October 2003
Abstract This paper presents the first study of standby power use and its saving potential in China. Standby power use refers to power consumed by appliances when they are switched off or are not providing their intended functions. Appliances in 28 urban Chinese homes were surveyed and standby power use was measured. The combined standby power use was about 29 W per home. However, many occupants unplug appliances when not in use, so standby energy use accounts for 50–200 kWh per year in an average urban home. Residential standby power consumption in China requires the electrical output equivalent of at least six 500 MW power plants. Levels of standby power use in Chinese homes are below those observed in developed countries but still high in part because Chinese appliances have higher standby than similar products in developed countries. Existing technologies are available to greatly reduce standby power at low costs. © 2003 Published by Elsevier B.V. Keywords: Standby power; Homes; China; Measurements; Conservation potential
1. Introduction Standby power use typically describes the power consumption of appliances when they are switched off or not providing their primary services. The most common appliances with standby power use are televisions, VCRs, microwave ovens, and all devices with external power supplies (such as chargers for mobile telephones). Any appliance with a remote control, such as room air conditioners and many audio products, will also consume standby power. Standby power use is small for each appliance; however, when aggregated, it represents a significant portion of household energy consumption. Several studies [1–8] have documented that standby power is about 20–90 W per home in developed nations, ranging from 4 to 10% of total residential electricity use. Standby power use is also responsible for a significant amount of global carbon emissions. Even though these appliances are off or not fulfilling their primary functions, their standby use is nevertheless responsible for about 1% of total carbon emissions in OECD countries. [5,9]. Reducing standby power use has been recognized by a grow-
∗ Corresponding author. Fax: +1-510-486-4673. E-mail address: [email protected] (A. Meier).
0378-7788/$ – see front matter © 2003 Published by Elsevier B.V. doi:10.1016/j.enbuild.2003.10.011
ing community of researchers and international agencies as one of the best greenhouse gas mitigation strategies because standby power use can be substantially reduced at relatively low costs. There is almost no information about standby power use in developing countries. Even if the levels of standby power draw for a particular appliance are similar to those found in developed countries, the ownership and usage patterns of those appliances will be different. This paper represents the first estimate of standby power use in China and the potential for reducing it.
2. Appliance ownership in China Over the last twenty years, appliance penetration has risen sharply in China (see Fig. 1). In 1980, few Chinese families had any electric appliances with the exception of radios and black and white television sets. By 1999, however, clothes washers were present in over 90% of urban Chinese homes; color television sets are present in nearly every urban household; and the ownership of refrigerators and room air-conditioners stands at 78 and 24%, respectively (State Statistical Bureau (SSB) [10]). Appliance ownership in rural households still lags behind that in urban households, however, the upward trend is similar.
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A. Meier et al. / Energy and Buildings 36 (2004) 1211–1216 Table 1 Summary statistics of standby power measurements
120
Saturation (%)
100
Clothes Washer Color TV Refrigerator AC
Product
Count Standby Power (W)
Air conditioner Amplifier Audio system Cooking fan Digital versatile disk (DVD) Microwave oven Refrigerator Rice cooker Television (TV) Video compact disk (VCD) Video cassette recorder (VCR)
32 2 5 1 1 5 12 1 31 16 1
Minimum Average Maximum
80 60 40 20 0 1980
1985
1990
1995
2000
Year
1.0 19 3.6 1.2 3.6 0.5 0.5 5.2 2.4 3.4 13
3.1 31.7 10.0 1.2 3.6 2.9 4.1 5.2 9.6 12.9 12.8
9.3 45 20 1.2 3.6 3.7 12 5.2 21 22 13
Fig. 1. Appliance saturations of major appliances in China.
3. Measurements of standby power use in urban Chinese homes Data presented in this paper were collected from an informal survey of 28 homes in Guangzhou, all belonging to staff of CEPREI Guangzhou Testing Laboratory, in December 2000. This was not a representative sample of Chinese urban homes; however, the focus of this survey was to rapidly obtain first-hand information on measured standby power consumption. The appliances in each home were inspected. If they had features generally associated with standby power use—remote control, digital displays, external power supplies, etc.—then their standby power use was measured. This initial survey focused on standby power use by larger appliances and ignored the smaller devices. For example, the surveyors did not measure cordless telephones, mobile telephones (or at least their chargers), and many types of computer equipment that may consume significant amounts of standby power. As a result, this survey significantly underestimates the actual number of appliances with standby power use and the total standby power per home. For this study, standby power use was considered to be the lowest power while connected to the electrical mains. Standby power draws are typically in the range of 1–10 W. Many watt-meters cannot accurately measure power use in this range. We used a meter with an accuracy of ±0.1 W in this range. Table 1 shows ownership and power consumption of major appliances with standby power features. Most Chinese air conditioners have standby power use because they need to respond to remote controls. Many new refrigerators have microprocessor controls that cause energy use even when the compressor is not operating. Even modern rice cookers have clocks, displays, and other advanced controls that draw standby power. Television sets and air conditioners are the most popular appliances; every family has at least one on average. Roughly two-thirds of the families own video players (VCD,
DVD, or VCR). Over 40% of the families surveyed have refrigerators (this is lower than urban average, probably because a large proportion of the families in this survey are young). About 20% of the families have stereo systems and microwave ovens. The highest standby power usages recorded are 45 W for amplifiers, 22 W for VCDs, 21 W for television sets, and 20 W for stereo systems. Due to their prevalence and high average standby power ratings, televisions and video players are the top two appliances that contribute to most of the standby power in these homes. There is also considerable variation in the standby power in the measured Chinese appliances. For instance, the lowest standby power recorded for television sets is 2.4 W, low enough to qualify for the Energy Star label, while the highest is over 20 W. Fig. 2 presents the distribution of TV and VCD standby power usage measured in this survey. Most TVs and VCD players in this sample have 6 W or higher standby power use. It is interesting to note that most VCD players have higher standby power use than TVs. The total household standby power measured in this survey is summarized in Fig. 3. The average standby power per household is 29 W, and the highest is 100 W. The majority of the households in this sample have a standby power between 20 and 50 W.
4. Estimates of annual standby energy use in China Standby energy consumption (Table 2) depends not only on measured, instantaneous, standby power usage of all Table 2 Standby energy consumption under three scenarios Scenario (hours plugged in per day)
Annual electricity consumption per household (kWh per year)
National electricity use (TW h per year)
20 10 5
200 100 50
25 13 6
A. Meier et al. / Energy and Buildings 36 (2004) 1211–1216
1213
14
12
Number of homes
10
TVs VCDs
8
6
4
2
0
0-3
3-6
6-9
9 - 12
12 - 15
15 - 18
18 - 21
21 - 24
Standby power (watts)
Fig. 2. Distribution of standby power use of TVs and VCDs in Chinese homes. 9 8
Number of homes
7 6 5 4 3 2 1 0 0 - 10 11 - 20 21 - 30 31 - 40 41 - 50 51 - 60 61 - 70 71 - 80 81 - 90
91 -100
Household total standby power (watts)
Fig. 3. Distribution of total standby power usage in the surveyed homes.
appliances, but also on how long each appliance spends in the standby mode. In most developed countries, these appliances are plugged in 24 h per day, so the calculation of annual energy consumption is straightforward. Anecdotal evidence suggests that time spent in standby mode in China is less than the 24 h per day because many Chinese families disconnect their TVs and other audio/video appliances by means of a switch on the power strip. In the past, this behavior was largely a safety measure to protect appliances against electricity supply disruptions and voltage fluctuations. Power delivery is now more reliable in Chinese cities,
so voltage spikes and potential damage to electrical equipment are much less of a concern today. Other appliances, such as cordless phones, are no doubt plugged in all day. Anecdotal evidence suggests that the practice of unplugging appliances is losing popularity, particularly among the younger generations of home owners. In the newly built homes, consideration of interior aesthetics often dictates the exclusion of visible power strips in the central entertainment station. And as their income levels rise, Chinese home owners are simply less inclined to lose the convenience of their remote controls.
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Given the uncertainty of time spent in standby mode, three scenarios were chosen to represent the range of possibilities: 5, 10, and 20 h per day, respectively. Based on such assumptions, estimates of average standby electricity consumption range from 50 to 200 kWh per month. This corresponds to 4–16% of average household electricity consumption in Guangzhou during a winter month. (It would be less in the summer because of higher air conditioning electricity use.) We believe that the actual situation probably corresponds to more than 10 h per day, that is, our middle assumption probably underestimates the actual standby electricity consumption. There are roughly 120 million households in urban China, so the total residential standby power consumption in China could range from 6 to 25 TW h per year. Even at the middle estimate, this power consumption is equivalent to the output of six 500 MW power plants. Rural households were not included in this estimate because we have no similar measurements. However, their contribution is probably much smaller than urban households because appliance ownership is much lower in rural China and many even lack access to electricity. Further measurements of standby power were undertaken in Beijing and Guangzhou during 2001. About 150 homes were studied. The analysis of the data is still underway but preliminary results indicate standby power use for these two cities is 33 and 38 W, respectively. This suggests that our results presented here are either conservative or that rapid growth is occurring.
5. Potential electricity savings and reductions in CO2 emissions Much of the standby power consumption estimated above can be eliminated through simple design changes in the appliances. Meier and Lebot [11] described some of these technologies and even proposed that standby in all devices could be reduced to about 1 W. The field measurements presented here suggest that Chinese appliances have on average higher standby power consumptions than similar products in Europe, Japan, or the United States. For example, Chinese television sets and video players consume on average 9.6 and 12.8 W, respectively, while similar units in Japanese homes consumed roughly half as much [2]. Although power reduction per appliance is modest, the aggregate impact for China as a whole could be substantial. To estimate the total savings through reducing standby power of Chinese appliances, three scenarios are constructed: the Best Available in China, the 3 and 1 W scenarios. The 3 and 1 W scenarios assume that standby power of Chinese appliances is limited to 3 and 1 W,1 respectively, while the Best
1 The 1 W scenario reflects the target set by IEA’s One Watt Initiative, which aims to limit standby power loss to under 1 watt by 2010.
Table 3 Energy savings estimates (TW h) from different scenarios of maximum standby power levels Scenario (hours plugged in per day)
20 10 5
Energy savings in different scenarios for standby power use (TW h per year) Best available in China
3 (W)
1 (W)
17 8.7 4.3
15 7.5 3.8
22 11 5.4
in China scenario takes the lowest observed standby power for each appliance product class as the target (Table 3). The choice of these three scenarios reflects the international practices and what China can realistically achieve in the near term. For example, the present Energy Star specification for televisions is 3 W [12], but models with 1 W are already available. Based on these assumptions, the potential energy savings in China from reducing standby power use in its appliances could range from 3.8 to 22 TW h per year. Even achieving the modest target of 3 W of standby power per appliance could lead to reductions of electricity consumption by 3.8 to 15 TW h per year. Such electricity savings correspond to a reduction of CO2 emissions of 5–19 million tons.
6. Discussion This is the first field measurement of standby power use in China. The survey was not representative because it focused solely on urban households and used a sample of convenience. Furthermore, the survey concentrated on major appliances and ignored many, smaller appliances that nevertheless have standby power use. Actual standby power use in the surveyed homes is likely to be higher than reported in this study. Nevertheless, the results are meaningful. The largest uncertainty lies not in the biased sample but in the number of hours that the units are plugged in and actually consuming standby power. We believe that standby energy use is responsible for about 10% of total electricity use in urban Chinese homes. Thus, standby already ranks among the five largest end-uses of electricity. There is strong evidence that it will grow rapidly as consumers buy more appliances that consume standby power and as consumers keep the appliances plugged in more hours each day. These synergistic trends could cause standby power use to be the fastest growing end-use of electricity in Chinese homes. This increasing electricity use translates directly into further investments in new electrical generating facilities and CO2 emissions. These estimates would be much higher if standby power use in office equipment were included. Meier [7] compiled all known field measurements of standby power use. Fig. 4 shows some of these studies and
A. Meier et al. / Energy and Buildings 36 (2004) 1211–1216
7. Conclusions
140
Average standby power per home (Watts)
1215
120 Europe China
100
North America Japan, Australia, & NZ China (preliminary results)
80
60
40
20
0 0
50
100
150
200
Number of homes in study
Fig. 4. Field measurements of standby power use in different countries.
China? position among them. While some larger studies have been undertaken in Europe, the study reported here is among the largest in the world. At 29 W, standby power use in China is much lower than found in similar studies in Japan, Australia, and the United States (typically above 60 W). This is not surprising because these countries have many more appliances with standby power. On the other hand, a significant fraction of Chinese homes already have standby equal to (or even exceeding) that found in European homes. There is also strong evidence that Chinese appliances have higher standby power use than similar appliances in developed countries. This suggests that reductions in standby power levels will be easier—and cheaper—to achieve than in developed countries. Chinese manufacturers already build low-standby products for export, so the technical capability is already present. More careful investigations of individual appliances will be needed to confirm the technical opportunities and costs of cutting standby power. Although China has begun creating minimum efficiency regulations for refrigerators and air conditioners, there are currently no regulations to limit standby power use. Recently China established a program to identify low standby products similar to the Energy Star program in the United States. In 2003 Chinese consumers were introduced to the problem of standby power use through an extensive series of newspaper and magazine articles. Nevertheless, these twin problems—lack of a means to identify low-standby products and lack of consumer awareness—hinder any market-based solution in the near future.
This first survey of standby power usage in urban Chinese homes demonstrated that standby power is already a significant end-use of electricity and cause of CO2 emissions. Our middle assumption regarding hours that the appliances are plugged in leads to standby electricity use of at least 100 kWh per year per household. Nationally, this translates to 13 TW h per year and over 16 million tons per year of CO2 . Standby power appears to be the fifth largest residential end-use of electricity and is growing rapidly as households acquire more appliances with standby power use. Our survey contains large uncertainties—such as omission of many smaller appliances with standby power use, and no information on the number of hours that the devices are plugged in—but it probably underestimates the actual electricity consumed in the standby mode in those homes. Standby power use in urban China is probably higher than estimated here because the surveyed homes consisted of younger, less mature, households than average. The national estimate of standby electricity use is low because it also excludes rural households. These rural households have less access to electricity and fewer appliances with standby power use, but the sheer number of households means that a small fraction can still have a high aggregate standby power use. Comparisons with studies in other countries suggest that large reductions in standby power are possible. If these reductions could be achieved, they would translate into avoided construction of thousands of megawatts of avoided generating capacity and million of tons of avoided CO2 emissions per year. This study has already had a significant impact on Chinese energy policy. The unexpectedly high levels of standby power usage observed in this survey caused the Chinese government to begin a much larger survey of standby power. (This will be reported in a future article when results are available.) In addition, the Chinese government initiated measures to reduce standby power. The first measure is a voluntary program to reduce standby power in televisions, including pressure on manufacturers to use export-quality technologies in domestic models. Further actions are being considered. In any event, standby power is likely to be an important component of electricity use in China and other developing countries.
Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies, of the U.S. Department of Energy under Contract No. DE-AC03 76SF00098, and by a grant from the Energy Foundation under grant number BG0012900.
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References [7] [1] L. Rainer, A. Meier, et al., Leaking electricity in homes. ACEEE Summer Study on energy efficiency in buildings, American Council for an Energy-Efficient Economy, Pacific Grove CA, 1996. [2] H. Nakagami, A. Tanaka, et al., Standby Electricity Consumption in Japanese Houses, in: Proceedings of the First International Conference on Energy Efficiency in Household Appliances, Florence (Italy), Association of Italian Energy Economics, 1997. [3] O. Sidler, Campagne de Mesures sur le Fonctionnement en Veille des Appareils Domestiques, ADEME, Sophia-Antipolis, France, 2000. [4] L. Harrington, P. Kleverlaan, Quantification of residential standby power consumption in Australia: results of recent survey work, Australian Greenhouse Office, Canberra, 2001. [5] International Energy Agency, Things That Go Blip in the Night: Standby Power and How to Limit It, International Energy Agency, Paris, France, 2001. [6] J. Vowles, B. Boardman, et al., Suspecting Standby? Domestic levels and the potential for household-level reductions in the UK, ECEEE
[8]
[9]
[10] [11]
[12]
Summer Study, European Council for An Energy Efficient Economy, Mandelieu, France, 2001. A. Meier, A worldwide review of standby power use in homes, in: Symposium on Highly Efficient Use of Energy and Reduction of Its Environmental Impact, Japan Society for the Promotion of Science, Osaka, Japan, 2002. J.P. Ross, A.K. Meier, Measurements of whole-house standby power consumption in California homes, Energy—The International Journal 27 (9) (2002) 861–868. B. Lebot, A. Meier, et al., Global implications of standby power use, in: Proceedings of the ACEEE Summer Study on Energy Efficiency in Buildings, Pacific Grove CA, American Council for An Energy Efficient Economy, 2000. State Statistical Bureau (SSB), China Statistical Yearbook, Beijing, 2000. A. Meier, B. Lebot, One watt initiative: a global effort to reduce leaking electricity, energy efficiency and CO2 reduction: the dimensions of the social challenge, European Council for an Energy Efficient Economy, Mandelieu, France, 1999. Energy Star Program, http://www.energystar.gov, United States Environmental Protection Agency, 2002.
Standby power use in Chinese homes Alan Meier a,∗ , Jiang Lin a , Jiang Liu b , Tienan Li c a
Lawrence Berkeley National Laboratory, University of California, Energy Analysis Department, Laboratory, Building 90, Room 2000, Berkeley, CA 94720, USA b CEPREI, Guangzhou, China c CECP, Beijing, China Received 28 April 2003; accepted 31 October 2003
Abstract This paper presents the first study of standby power use and its saving potential in China. Standby power use refers to power consumed by appliances when they are switched off or are not providing their intended functions. Appliances in 28 urban Chinese homes were surveyed and standby power use was measured. The combined standby power use was about 29 W per home. However, many occupants unplug appliances when not in use, so standby energy use accounts for 50–200 kWh per year in an average urban home. Residential standby power consumption in China requires the electrical output equivalent of at least six 500 MW power plants. Levels of standby power use in Chinese homes are below those observed in developed countries but still high in part because Chinese appliances have higher standby than similar products in developed countries. Existing technologies are available to greatly reduce standby power at low costs. © 2003 Published by Elsevier B.V. Keywords: Standby power; Homes; China; Measurements; Conservation potential
1. Introduction Standby power use typically describes the power consumption of appliances when they are switched off or not providing their primary services. The most common appliances with standby power use are televisions, VCRs, microwave ovens, and all devices with external power supplies (such as chargers for mobile telephones). Any appliance with a remote control, such as room air conditioners and many audio products, will also consume standby power. Standby power use is small for each appliance; however, when aggregated, it represents a significant portion of household energy consumption. Several studies [1–8] have documented that standby power is about 20–90 W per home in developed nations, ranging from 4 to 10% of total residential electricity use. Standby power use is also responsible for a significant amount of global carbon emissions. Even though these appliances are off or not fulfilling their primary functions, their standby use is nevertheless responsible for about 1% of total carbon emissions in OECD countries. [5,9]. Reducing standby power use has been recognized by a grow-
∗ Corresponding author. Fax: +1-510-486-4673. E-mail address: [email protected] (A. Meier).
0378-7788/$ – see front matter © 2003 Published by Elsevier B.V. doi:10.1016/j.enbuild.2003.10.011
ing community of researchers and international agencies as one of the best greenhouse gas mitigation strategies because standby power use can be substantially reduced at relatively low costs. There is almost no information about standby power use in developing countries. Even if the levels of standby power draw for a particular appliance are similar to those found in developed countries, the ownership and usage patterns of those appliances will be different. This paper represents the first estimate of standby power use in China and the potential for reducing it.
2. Appliance ownership in China Over the last twenty years, appliance penetration has risen sharply in China (see Fig. 1). In 1980, few Chinese families had any electric appliances with the exception of radios and black and white television sets. By 1999, however, clothes washers were present in over 90% of urban Chinese homes; color television sets are present in nearly every urban household; and the ownership of refrigerators and room air-conditioners stands at 78 and 24%, respectively (State Statistical Bureau (SSB) [10]). Appliance ownership in rural households still lags behind that in urban households, however, the upward trend is similar.
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A. Meier et al. / Energy and Buildings 36 (2004) 1211–1216 Table 1 Summary statistics of standby power measurements
120
Saturation (%)
100
Clothes Washer Color TV Refrigerator AC
Product
Count Standby Power (W)
Air conditioner Amplifier Audio system Cooking fan Digital versatile disk (DVD) Microwave oven Refrigerator Rice cooker Television (TV) Video compact disk (VCD) Video cassette recorder (VCR)
32 2 5 1 1 5 12 1 31 16 1
Minimum Average Maximum
80 60 40 20 0 1980
1985
1990
1995
2000
Year
1.0 19 3.6 1.2 3.6 0.5 0.5 5.2 2.4 3.4 13
3.1 31.7 10.0 1.2 3.6 2.9 4.1 5.2 9.6 12.9 12.8
9.3 45 20 1.2 3.6 3.7 12 5.2 21 22 13
Fig. 1. Appliance saturations of major appliances in China.
3. Measurements of standby power use in urban Chinese homes Data presented in this paper were collected from an informal survey of 28 homes in Guangzhou, all belonging to staff of CEPREI Guangzhou Testing Laboratory, in December 2000. This was not a representative sample of Chinese urban homes; however, the focus of this survey was to rapidly obtain first-hand information on measured standby power consumption. The appliances in each home were inspected. If they had features generally associated with standby power use—remote control, digital displays, external power supplies, etc.—then their standby power use was measured. This initial survey focused on standby power use by larger appliances and ignored the smaller devices. For example, the surveyors did not measure cordless telephones, mobile telephones (or at least their chargers), and many types of computer equipment that may consume significant amounts of standby power. As a result, this survey significantly underestimates the actual number of appliances with standby power use and the total standby power per home. For this study, standby power use was considered to be the lowest power while connected to the electrical mains. Standby power draws are typically in the range of 1–10 W. Many watt-meters cannot accurately measure power use in this range. We used a meter with an accuracy of ±0.1 W in this range. Table 1 shows ownership and power consumption of major appliances with standby power features. Most Chinese air conditioners have standby power use because they need to respond to remote controls. Many new refrigerators have microprocessor controls that cause energy use even when the compressor is not operating. Even modern rice cookers have clocks, displays, and other advanced controls that draw standby power. Television sets and air conditioners are the most popular appliances; every family has at least one on average. Roughly two-thirds of the families own video players (VCD,
DVD, or VCR). Over 40% of the families surveyed have refrigerators (this is lower than urban average, probably because a large proportion of the families in this survey are young). About 20% of the families have stereo systems and microwave ovens. The highest standby power usages recorded are 45 W for amplifiers, 22 W for VCDs, 21 W for television sets, and 20 W for stereo systems. Due to their prevalence and high average standby power ratings, televisions and video players are the top two appliances that contribute to most of the standby power in these homes. There is also considerable variation in the standby power in the measured Chinese appliances. For instance, the lowest standby power recorded for television sets is 2.4 W, low enough to qualify for the Energy Star label, while the highest is over 20 W. Fig. 2 presents the distribution of TV and VCD standby power usage measured in this survey. Most TVs and VCD players in this sample have 6 W or higher standby power use. It is interesting to note that most VCD players have higher standby power use than TVs. The total household standby power measured in this survey is summarized in Fig. 3. The average standby power per household is 29 W, and the highest is 100 W. The majority of the households in this sample have a standby power between 20 and 50 W.
4. Estimates of annual standby energy use in China Standby energy consumption (Table 2) depends not only on measured, instantaneous, standby power usage of all Table 2 Standby energy consumption under three scenarios Scenario (hours plugged in per day)
Annual electricity consumption per household (kWh per year)
National electricity use (TW h per year)
20 10 5
200 100 50
25 13 6
A. Meier et al. / Energy and Buildings 36 (2004) 1211–1216
1213
14
12
Number of homes
10
TVs VCDs
8
6
4
2
0
0-3
3-6
6-9
9 - 12
12 - 15
15 - 18
18 - 21
21 - 24
Standby power (watts)
Fig. 2. Distribution of standby power use of TVs and VCDs in Chinese homes. 9 8
Number of homes
7 6 5 4 3 2 1 0 0 - 10 11 - 20 21 - 30 31 - 40 41 - 50 51 - 60 61 - 70 71 - 80 81 - 90
91 -100
Household total standby power (watts)
Fig. 3. Distribution of total standby power usage in the surveyed homes.
appliances, but also on how long each appliance spends in the standby mode. In most developed countries, these appliances are plugged in 24 h per day, so the calculation of annual energy consumption is straightforward. Anecdotal evidence suggests that time spent in standby mode in China is less than the 24 h per day because many Chinese families disconnect their TVs and other audio/video appliances by means of a switch on the power strip. In the past, this behavior was largely a safety measure to protect appliances against electricity supply disruptions and voltage fluctuations. Power delivery is now more reliable in Chinese cities,
so voltage spikes and potential damage to electrical equipment are much less of a concern today. Other appliances, such as cordless phones, are no doubt plugged in all day. Anecdotal evidence suggests that the practice of unplugging appliances is losing popularity, particularly among the younger generations of home owners. In the newly built homes, consideration of interior aesthetics often dictates the exclusion of visible power strips in the central entertainment station. And as their income levels rise, Chinese home owners are simply less inclined to lose the convenience of their remote controls.
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Given the uncertainty of time spent in standby mode, three scenarios were chosen to represent the range of possibilities: 5, 10, and 20 h per day, respectively. Based on such assumptions, estimates of average standby electricity consumption range from 50 to 200 kWh per month. This corresponds to 4–16% of average household electricity consumption in Guangzhou during a winter month. (It would be less in the summer because of higher air conditioning electricity use.) We believe that the actual situation probably corresponds to more than 10 h per day, that is, our middle assumption probably underestimates the actual standby electricity consumption. There are roughly 120 million households in urban China, so the total residential standby power consumption in China could range from 6 to 25 TW h per year. Even at the middle estimate, this power consumption is equivalent to the output of six 500 MW power plants. Rural households were not included in this estimate because we have no similar measurements. However, their contribution is probably much smaller than urban households because appliance ownership is much lower in rural China and many even lack access to electricity. Further measurements of standby power were undertaken in Beijing and Guangzhou during 2001. About 150 homes were studied. The analysis of the data is still underway but preliminary results indicate standby power use for these two cities is 33 and 38 W, respectively. This suggests that our results presented here are either conservative or that rapid growth is occurring.
5. Potential electricity savings and reductions in CO2 emissions Much of the standby power consumption estimated above can be eliminated through simple design changes in the appliances. Meier and Lebot [11] described some of these technologies and even proposed that standby in all devices could be reduced to about 1 W. The field measurements presented here suggest that Chinese appliances have on average higher standby power consumptions than similar products in Europe, Japan, or the United States. For example, Chinese television sets and video players consume on average 9.6 and 12.8 W, respectively, while similar units in Japanese homes consumed roughly half as much [2]. Although power reduction per appliance is modest, the aggregate impact for China as a whole could be substantial. To estimate the total savings through reducing standby power of Chinese appliances, three scenarios are constructed: the Best Available in China, the 3 and 1 W scenarios. The 3 and 1 W scenarios assume that standby power of Chinese appliances is limited to 3 and 1 W,1 respectively, while the Best
1 The 1 W scenario reflects the target set by IEA’s One Watt Initiative, which aims to limit standby power loss to under 1 watt by 2010.
Table 3 Energy savings estimates (TW h) from different scenarios of maximum standby power levels Scenario (hours plugged in per day)
20 10 5
Energy savings in different scenarios for standby power use (TW h per year) Best available in China
3 (W)
1 (W)
17 8.7 4.3
15 7.5 3.8
22 11 5.4
in China scenario takes the lowest observed standby power for each appliance product class as the target (Table 3). The choice of these three scenarios reflects the international practices and what China can realistically achieve in the near term. For example, the present Energy Star specification for televisions is 3 W [12], but models with 1 W are already available. Based on these assumptions, the potential energy savings in China from reducing standby power use in its appliances could range from 3.8 to 22 TW h per year. Even achieving the modest target of 3 W of standby power per appliance could lead to reductions of electricity consumption by 3.8 to 15 TW h per year. Such electricity savings correspond to a reduction of CO2 emissions of 5–19 million tons.
6. Discussion This is the first field measurement of standby power use in China. The survey was not representative because it focused solely on urban households and used a sample of convenience. Furthermore, the survey concentrated on major appliances and ignored many, smaller appliances that nevertheless have standby power use. Actual standby power use in the surveyed homes is likely to be higher than reported in this study. Nevertheless, the results are meaningful. The largest uncertainty lies not in the biased sample but in the number of hours that the units are plugged in and actually consuming standby power. We believe that standby energy use is responsible for about 10% of total electricity use in urban Chinese homes. Thus, standby already ranks among the five largest end-uses of electricity. There is strong evidence that it will grow rapidly as consumers buy more appliances that consume standby power and as consumers keep the appliances plugged in more hours each day. These synergistic trends could cause standby power use to be the fastest growing end-use of electricity in Chinese homes. This increasing electricity use translates directly into further investments in new electrical generating facilities and CO2 emissions. These estimates would be much higher if standby power use in office equipment were included. Meier [7] compiled all known field measurements of standby power use. Fig. 4 shows some of these studies and
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7. Conclusions
140
Average standby power per home (Watts)
1215
120 Europe China
100
North America Japan, Australia, & NZ China (preliminary results)
80
60
40
20
0 0
50
100
150
200
Number of homes in study
Fig. 4. Field measurements of standby power use in different countries.
China? position among them. While some larger studies have been undertaken in Europe, the study reported here is among the largest in the world. At 29 W, standby power use in China is much lower than found in similar studies in Japan, Australia, and the United States (typically above 60 W). This is not surprising because these countries have many more appliances with standby power. On the other hand, a significant fraction of Chinese homes already have standby equal to (or even exceeding) that found in European homes. There is also strong evidence that Chinese appliances have higher standby power use than similar appliances in developed countries. This suggests that reductions in standby power levels will be easier—and cheaper—to achieve than in developed countries. Chinese manufacturers already build low-standby products for export, so the technical capability is already present. More careful investigations of individual appliances will be needed to confirm the technical opportunities and costs of cutting standby power. Although China has begun creating minimum efficiency regulations for refrigerators and air conditioners, there are currently no regulations to limit standby power use. Recently China established a program to identify low standby products similar to the Energy Star program in the United States. In 2003 Chinese consumers were introduced to the problem of standby power use through an extensive series of newspaper and magazine articles. Nevertheless, these twin problems—lack of a means to identify low-standby products and lack of consumer awareness—hinder any market-based solution in the near future.
This first survey of standby power usage in urban Chinese homes demonstrated that standby power is already a significant end-use of electricity and cause of CO2 emissions. Our middle assumption regarding hours that the appliances are plugged in leads to standby electricity use of at least 100 kWh per year per household. Nationally, this translates to 13 TW h per year and over 16 million tons per year of CO2 . Standby power appears to be the fifth largest residential end-use of electricity and is growing rapidly as households acquire more appliances with standby power use. Our survey contains large uncertainties—such as omission of many smaller appliances with standby power use, and no information on the number of hours that the devices are plugged in—but it probably underestimates the actual electricity consumed in the standby mode in those homes. Standby power use in urban China is probably higher than estimated here because the surveyed homes consisted of younger, less mature, households than average. The national estimate of standby electricity use is low because it also excludes rural households. These rural households have less access to electricity and fewer appliances with standby power use, but the sheer number of households means that a small fraction can still have a high aggregate standby power use. Comparisons with studies in other countries suggest that large reductions in standby power are possible. If these reductions could be achieved, they would translate into avoided construction of thousands of megawatts of avoided generating capacity and million of tons of avoided CO2 emissions per year. This study has already had a significant impact on Chinese energy policy. The unexpectedly high levels of standby power usage observed in this survey caused the Chinese government to begin a much larger survey of standby power. (This will be reported in a future article when results are available.) In addition, the Chinese government initiated measures to reduce standby power. The first measure is a voluntary program to reduce standby power in televisions, including pressure on manufacturers to use export-quality technologies in domestic models. Further actions are being considered. In any event, standby power is likely to be an important component of electricity use in China and other developing countries.
Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies, of the U.S. Department of Energy under Contract No. DE-AC03 76SF00098, and by a grant from the Energy Foundation under grant number BG0012900.
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