Applied Energy 83 (2006)

Transcription

1 Applied Energy 83 (26) APPLIED ENERGY Effectiveness of an energy-consumption information system on energy savings in residential houses based on monitored data Tsuyoshi Ueno *, Fuminori Sano, Osamu Saeki, Kiichiro Tsuji Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka , Japan Available online 14 June 25 Abstract Reducing energy demand in the residential sector is an important problem worldwide. This study focused on the awareness of residents to energy conservation and on the potential of reducing energy demand through energy-saving activities. To carry out quantitative analysis, an on-line interactive energy consumption information system for motivating energy-saving activities is constructed, and it was installed in nine residential houses. By utilizing data of measured power consumption, ambient and room temperatures before and after installation of the system, and the responses of the residents to the system, its effectiveness was evaluated. Major findings were as follows: (1) installation of the system led to a 9% reduction in power consumption, (2) comparisons of daily-load curves and load-duration curves for each appliance, before and after installation, revealed various energy-saving behaviors of the household members such as the reduction of standby power and better control of appliance operation, and (3) energy-conservation awareness affected not only the power consumption of the appliances explicitly shown on the display monitor, but also other household appliances. Ó 25 Elsevier Ltd. All rights reserved. Keywords: Energy information; Residential house; Energy-saving potential; Monitoring; Energy consumption * Corresponding author. Tel.: ; fax: address: tsuyoshi@polux.pwr.eng.osaka-u.ac.jp (T. Ueno) /$ - see front matter Ó 25 Elsevier Ltd. All rights reserved. doi:1.116/j.apenergy

2 T. Ueno et al. / Applied Energy 83 (26) Introduction In recent years, social concern over environmental problems, such as increasing atmospheric temperatures and destruction of the ozone layer, has increased on a global scale. In the future, increased efficiency of energy systems and reduced end-use energy demand will be important in attaining the 6% curtailment of greenhousegases targeted by the Kyoto Protocol. Reduced energy consumption in the residential sector is particularly important, because energy demand in this sector is notably increasing unlike in the industrial sector. For this purpose, improvements in home insulation and the efficiency of electric appliances are vitally important and new systems such as HEMS (home-energy management system) [1] and ECHONET (energy conservation and homecare network) [2], which control appliances through a domestic network, have been developed. Another possibility is to induce energy saving by providing household members with information on actual domestic energy-consumption. A number of researches have been conducted with regards to this; for example, Newborough [3,4] analyzed the effectiveness of an appliance-specific display showing the energy consumption for cooking, and classified the features necessary for displaying energy information [5]. Brandon [6,7] analyzed the most effective energy-saving technique among several feedback methods using, for example, computers, leaflets, etc. Egan [8] investigated the relationship between different display formats and the reaction to each from informants. The Shoene-navi (energy-saving navigator) produced by the Energy Conservation Center in Japan displays the power consumption of an entire household [9]. Furthermore, Osaka Gas developed an energy-consumption information service in an experimental apartment house called NEXT21. This service included measurements of not only electric power, and heated-water supply, but also display graphs of consumption charges on a web browser [1]. However, in these researches, the energy awareness behaviors of the consumers induced by the energy information systems were not discussed in detail. The authors carried out a monitoring project in which end-use electric power and room temperature were measured every 3 min for residential houses in a newlydeveloped town in suburban Kyoto, Japan [11]. As part of this project, an on-line Energy Consumption Information System (hereafter referred to as ECOIS) was developed and installed in some of the monitored houses [12]. The main purposes of the study were to analyze: (1) how consumers are interested in their household energy-consumption, (2) how consumers changed their behaviors toward energy consumption and how power consumption changed after the installation of ECOIS, and (3) whether there are any energy-saving effects of ECOIS. 2. Construction of an energy-consumption information system 2.1. The monitoring and information system Fig. 1 shows the configuration of ECOIS, which consists of monitoring and distribution components. The monitoring component includes a load-survey meter

3 168 T. Ueno et al. / Applied Energy 83 (26) Monitoring Component Distribution Component Osaka Univ. Monitoring Server Distribution Server Electric Power Monitored Data WHM Telephone Line LSM Processed Data Telephone Line Inquiry/Log of the system NCU Residential House Information Terminal WHM: Watt Hour Meter LSM: Load Survey Meter EUM: End Use Meter NCU: Network Control Unit EUM EUM Fig. 1. Configuration of ECOIS. (LSM) that measures electric-power consumption for the entire house, and an enduse meter (EUM) that measures electric-power consumption for each home appliance. Both measure power consumption at intervals of 3 min. The measured data were sent to the network control unit (NCU) through distribution lines throughout the house. Data were then collected through telephone lines, every night, by a computer in the authorõs laboratory at Osaka University. The distribution component includes a laboratory-based computer which distributes data to the information terminal in each house by . The logs of operation of the information terminal and responses of the consumers to the energy tips were sent to the distribution server every morning. Here, operation of the information terminal means pressing of buttons on the screen of a terminal, namely, a B5-sized laptop computer, by the customer Design of the information terminal Fig. 2 shows the composition of the display on the information terminal with an example of the graphs that can be drawn on the screen. Although various display methods can be considered effective for providing energy-consumption information, conciseness has a big influence on the overall effectiveness of the display methods. Hence, the composition of the display needs to be designed carefully. The following were taken into consideration during the design of the ECOIS display: Simple access to the detailed data. A number of buttons are properly located on a single display picture, and only a mouse is required in order to access various functions and more detailed data. The main graph area is located at the centre

4 T. Ueno et al. / Applied Energy 83 (26) Fig. 2. Display picture on the information terminal (translated into English). of the display picture, while windows displaying energy-saving tips and information on electricity charge are located below and to the right of the main graph area, respectively. Table 1 shows the various graphs that can be displayed, and Table 1 The buttons and corresponding graphs Buttons on the right-hand side of the main graph area Buttons below the main graph area Daily Each appliance Daily load-curve (each appliance) 1 days Daily changes in consumption over a 1-day period (each appliance) Comparison Comparison with past data (each appliance) Electricity charge of whole house Daily load-curve (whole house) Daily changes in consumption over a 1-day period (whole house) Comparison with past data (whole house) Percentage of the electricityconsumption charge Percentage of daily power-consumption of each appliance Daily changes in the percentage of power consumption over a 1-day period

5 17 T. Ueno et al. / Applied Energy 83 (26) Fig. 3. Examples of the graphs (translated into English). (a) Daily load curve (whole house). (b) Daily changes in consumption over a 1-day period (whole house). (c) Percentage of daily power-consumption of each appliance. (d) Comparisons with past data. Fig. 3 shows examples of the graphs. Note that the measured power-consumption data are displayed in terms of Japanese Yen so that residents can understand it easily. Provision of useful information for residents to save energy. While displaying a graph of each appliance, energy-saving tips are displayed on the message window. Each piece of advice urges the customer to press one of following three response buttons: [Yes], [I will try] and [Neither]. Capability of recording operation of the information terminal. When analyzing the awareness of consumers of energy consumption and of energy-saving potential, information on how interested each consumer is in the power consumption of each appliance and how these interests change over time are very important. Hence, operation of all buttons and the responses to each tip were recorded. 3. Effectiveness of ECOIS installation 3.1. ECOIS experiment The ECOIS experiment was carried out by installing information terminals to nine residential-houses. Monitoring was commenced in February 2 and information terminals were installed on 18 and 2 January 22. Each household included a married couple with 1 3 children.

6 3.2. Frequency of responses Fig. 4 shows the number of total operations (button pressings) and responses to energy-saving tips per day averaged over the nine households. It is clear that the number of total operations was very large immediately after installation, after which it decreased gradually. Table 2 shows the number of operations of buttons for selecting graphs over the experimental period. In both [each appliance] and [whole house] consumptiongraphs, the number of [daily] operations were larger than those of [1 days], which suggests that the participants were more interested in daily-load curves, which are more detailed than the total value of each day. [1 days] graphs of [percentage of the electricity consumption charge] and [comparison] graphs were displayed much less. It turns out that the number of operations for each graph greatly depends on its comprehensiveness and interest in each component Changes in power consumption T. Ueno et al. / Applied Energy 83 (26) To evaluate the effect of an ECOIS installation on power consumption, consumptions in two periods defined as before and after installation were compared. Fig. 4. Number of operations by the residents. Table 2 Number of operations (i.e. of pressing buttons) Buttons on the right-hand side of the main graph area Buttons below the main graph area Each appliance Electricity charge of whole house Daily days Comparisons Summation over the entire experiment for the nine houses. Percentage of the electricity-consumption charge

7 172 T. Ueno et al. / Applied Energy 83 (26) Here, 4 weekdays before installation of the ECOIS was defined as before installation, and 4 weekdays after installation was defined as after installation ; weekdays means any day except Saturday, Sunday, national holidays, the end and beginning of the year. To evaluate power consumption before and after installation impartially, the evaluation periods were limited to weekdays only. A questionnaire survey was used to check that no changes in the number of household individuals, for example, as a result of a business trip or hospitalization, or changes in the rooms used occurred. Consequently, power consumption of the whole household was reduced on average by about 9% across eight households; power consumption of household no. 9 was not measured due to a photovoltaic system. The average ambient temperatures before and after installation were 6.4 and 6.8 C, respectively. Generally, the power consumption of the whole household increases with the fall in ambient temperature in winter; hence, it is thought that the true effect was more than this 9% value. In a later section, it will be concretely shown what kinds of actions were taken by the residents by using the daily-load curves and load-duration curves of each appliance Energy-saving activities for space heating Fig. 5 shows the daily power-consumption for heating the living room and other rooms (household total) before and after an ECOIS installation. Power consumptions of heaters for freeze protection and standby power were removed, since they had no direct relationship to energy for space heating; the standby-power consumption of the appliances is described in Section 3.7. Power consumption for heating the living room was a little more than 5% of the total power-consumption for heating the whole house, averaged over nine houses. Power consumption for heating the living room after installation became about 77% of that before installation, and became about 84% in other rooms. Although city gas and kerosene are consumed for space heating, the increases in city gas and kerosene consumption for space heating after installation of ECOIS could not be estimated because city gas and kerosene consumptions were not measured. Fig. 6 shows the average temperatures of the living rooms in each house during room heating before and after installation. The room temperature after installation fell compared to before installation in many households. The reasons for this include the following: (1) change in heating appliances employed, (2) change in the set-up or output of appliances, (3) a fall of ambient temperature, and (4) reduced heating-time. As shown in Fig. 6, room temperatures during heating of each household differed from one another. The difference in room temperatures caused by an ECOIS installation was smaller than the difference between households. The reason for this is thought to be because changes in the appliances used and operation of these appliances were in the range that people could permit. Fig. 7 shows the relationship between the ratio of hours spent on space heating after an ECOIS installation to the ratio before installation and also the ratio of power consumption after an ECOIS installation to that before installation, both

8 T. Ueno et al. / Applied Energy 83 (26) Daily Power Consumption [kwh] Before ECOIS Installation After ECOIS Installation No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8 No.9 Ave. Household No. :Living Room Fig. 5. Power consumption of space heating before and after the ECOIS installation. Fig. 6. Temperature in the living rooms of each household. for the living room. As is clear from Fig. 7, the above two ratios remained similar in five houses, the ratio of power consumption became smaller than the ratio of hours for space heating in the other four houses. The reason for this was thought to be because the appliances used for space heating changed before and after installation: hence consumers were able to reduce the power consumption without reducing the hours for space heating. In household no. 5, a gas fan-heater and hot carpet were mainly used in the living room. Fig. 8(a) shows the operation days at 3-min intervals of these appliances before and after installation: here, operation days means the number of days consumers used a particular appliance at 3-min intervals during the evaluation periods. The load pattern of the hot carpet was almost equal in all time zones,

9 174 T. Ueno et al. / Applied Energy 83 (26) Fig. 7. Relationship between the ratios of hours and power consumption of heating before and after ECOIS installation. Fig. 8. Changes in the space-heating patterns in the living rooms before and after an ECOIS installation. although the operation days around 21: decreased significantly after installation. On the other hand, the gas fan-heater almost ceased to be used during the daytime after installation, even though it was operated for half the number of days before installation. Fig. 8(b) shows the operation days at 3-min intervals for an oil fanheater and hot carpet in the living room of household no. 7 before and after installation. The hot carpet ceased to be used after installation, while the load pattern of the oil fan-heater remained relatively unchanged during all time zones except around midnight. The room temperatures of the living rooms in households no. 5 and 7 during space heating fell by about 1 C, and comfort of their houses decreased a little. Fig. 9 shows the operation days at 3-min intervals of the heating appliances in the living room of household no. 2. While the operation days of the heat pump and hot carpet decreased after installation, the operation days of the gas fan-heater increased. City gas and kerosene consumption might increase even if the power con-

10 T. Ueno et al. / Applied Energy 83 (26) Fig. 9. Changes in the space-heating patterns in the living room of household No. 2 before and after an ECOIS installation. sumption is reduced by changes in the actions of consumers. As a result, the total energy-consumption for space heating might increase. This shows that, when displaying energy information, it is desirable to display simultaneously not only electric power but also other energy use such as of city gas Changes in the load pattern of television sets This section shows the changes in load patterns of T.V.s in the living rooms of each house after ECOIS installations. Fig. 1(a) shows the daily power-consumption during standby and during operation of the T.V. sets in each household, and Fig. 1(b) shows the daily hours of operation, standby and disconnection from the outlet. On average, the power consumption during operation after an ECOIS installation became about 95% of that before installation, with about 7 15% variation across households. The hours of operation after installation also became about 95% of that before installation. Fig. 1. Load patterns of television sets in the living rooms of each household. (a) Power consumption before and after an ECOIS installation. (b) Daily hours of operation, standby and disconnection before and after an ECOIS installation.

11 176 T. Ueno et al. / Applied Energy 83 (26) Operation Days[Day/4Days] (a) Before ECOIS Installation After ECOIS Installation Time [h] Electric Power [W] (b) Time Before the Installation After the Installation Fig. 11. Changes in the power consumption of the television set in household No. 6 before and after an ECOIS installation. (a) Operation days for 3-min intervals. (b) Load-duration curves. The operation days and load-duration curve of the T.V. in household no. 6 are shown in Fig. 11. After installation of an ECOIS, the number of operation days remained unchanged in the morning and evening, but they decreased in the daytime and nighttime. The resultant load-duration curve is shown in Fig. 11(b) in which the reduced hours of operation are shown. Consumers watch television to acquire useful information, thus reducing time for watching is not desirable as one of the possible energy-saving alternatives since it decreases consumersõ comfort. On the other hand, making sure to turn the television off when not being watched by anyone is an effective energy-saving method, because it does not decrease the consumerõs comfort Changes in the load pattern of refrigerators The daily power-consumptions of seven refrigerators and one freezer were measured before and after an ECOIS installation (Fig. 12). Although consumers said Daily Power Consumption[kWh] No.1 No.2 No.4 No.5 Before ECOIS Installation After ECOIS Installation No.6 No.7 No.9 No.2 Household No. Freezer Fig. 12. Power consumptions of seven refrigerators and one freezer before and after an ECOIS installation.

12 T. Ueno et al. / Applied Energy 83 (26) Electric Power [W] (a) Before ECOIS Installation After ECOIS Installation Time [h] Daily- load curves Electric Power [W] (b) Before ECOIS Installation After ECOIS Installation Time Load-duration curves Fig. 13. Changes in the power consumption of the refrigerator in household No. 2 before and after an ECOIS installation. (a) Daily-load curves. (b) Load-duration curves. they begun to take more care not to leave the refrigerator/freezer door open unnecessarily after installation, a clear change in power consumption as a result was not identified because the effect was very small. However, refrigeration capabilities (temperature setting) were changed for two refrigerators (households no. 2 and 5) and for the freezer (household no. 2) after installation, and significant reductions in power consumption were observed. Fig. 13 shows the daily load-curves and load-duration curves of the refrigerator of household no. 2 before and after an ECOIS installation. Changes in the loadduration curves showed that the power consumption decreased over all time zones. Refrigerators and freezers are always automatically operated, and their power consumption is very large. However, significant energy-saving effects can be expected by adjustments of the temperature setting, which is very easy and not necessary to repeat. However, this option should be chosen with care by considering the amounts of contents and circumambient temperature of the refrigerator, since this activity could result in undesirable changes of the environment inside the refrigerator Changes in the power consumption during standby This section describes the changes in power consumption when the appliances are not-in-use. The so-called standby power of an electric appliance is the power consumption during the period when it is not in use by any of the household members, and it is defined, for example, by the International Energy Agency [13]. Standby power has received much attention in the last 1 years since it represents an apparent potential for energy saving through improved control circuits or appliance usage [14,15]. Power consumptions for appliances with the function of keeping warm, for example, an electric pot or a rice cooker, are not included in the standby power. However, these appliances consume power when they are not in use, and once a consumer becomes aware of the power consumption, the consumer tends to treat these appliances as if they used standby power.

13 178 T. Ueno et al. / Applied Energy 83 (26) Table 3 Appliances consuming standby power End-use purposes Appliance Number of appliances that consume standby power Number of appliances whose standby power was reduced by method 1 Space heating Heat pump 3 2 Gas fan-heater 1 Oil fan-heater 1 1 Cooking Microwave oven 2 2 Electric rice-cooker 1 Heated water-supply Gas water-heater 11 Television Television a CATV reciver 3 1 Stero recorter 2 1 Personal computer 5 2 Telephone 1 a Including peripherals. Number of appliances whose standby power was reduced by method 2 Standby-power consumption was identified for 39 appliances, 1 and the power consumption for keeping warm was identified for nine appliances among 137 electric appliances which were monitored before and after an ECOIS installation. The methods for reducing the standby power of an appliance are: (1) disconnection from the outlet when not in use, and (2) changing the mode of the appliance during standby to a mode of lower power-consumption. Table 3 shows the number of appliances that consume standby power, and the number of each appliance whose standby power was reduced by the above two methods. Although method 1 was performed with various appliances, it was hard to perform for those appliances with functions that consumers considered indispensable (e.g., a timer on a video), or those located out of reach. Method 2 was available only for appliances with several standby modes; hence it was applied only to T.V.s as shown in Table 3. Fig. 14 shows the load duration curves of a stereo recorder in household no. 3 and of a T.V. in household no. 8. Method 1 was applied to the stereo recorder and was disconnected from the outlet when not in use. Method 2 was applied to the T.V. and the standby mode was changed. Table 4 shows the number of appliances that consume electric-power to keep warm and the number of those for which the hours for keeping warm were reduced. Fig. 15 shows the load-duration curves of an electric rice-cooker in household no. 7 1 Since standby power is not very large, the measurement system used in this monitoring project is not necessarily appropriate for identifying standby power exactly. Here, the accumulated power (kwh) identified by the measurement device is considered to represent the standby power.

14 T. Ueno et al. / Applied Energy 83 (26) (a) Electric Power [W] Before ECOIS Installation After ECOIS Installation Time Electric Power [W] (b) Before ECOIS Installation After ECOIS Installation Time Standby mode change Fig. 14. Load-duration curves showing the reductions in standby-power after an ECOIS installation for: (a) a stereo recorder in household no. 3 and (b) a television in household no. 8. Table 4 Appliances requiring heating End-use purpose Appliance Number of appliances that consume power to keep warm Cooking Electric pot 2 2 Electric rice-cooker 4 2 Heated toilet 3 2 Number of appliances for which the hours required to keep them warm were reduced Electric Power [W] (a) Before ECOIS Installation After ECOIS Installation Time (b) Electric Power [W] Before ECOIS Installation After ECOIS Installation Time Fig. 15. Load-duration curves showing the reductions in electric power consumed for heating after an ECOIS installation in: (a) an electric rice-cooker in household no. 7 and (b) a heated toilet in household no. 3. and a heated toilet in household no. 3. The hours of keeping warm the rice cooker after boiling rice was reduced, and the heated toilet was disconnected from the outlet at midnight or when going out. Fig. 16 shows the daily changes of the time when disconnected from the outlet for the electric rice-cooker and the heated toilet before and after installation of an ECOIS. The number of non-connected hours did not change very much for the electric rice-cooker after installation, but this change lasted over the monitored period. On the other hand, the hours of disconnection increased

15 18 T. Ueno et al. / Applied Energy 83 (26) Time When Disconnected from the Outlet [h] Heated Toilet Electric Rice Cooker Days from ECOIS Installation (Weekdays Only) Fig. 16. Daily changes in the time when disconnected after an ECOIS installation for an electric ricecooker and heated toilet. right after installation but decreased several weeks after installation for the heated toilet. The energy-saving action once performed did not last long since the consumerõs comfort reduced Energy awareness for the appliances not displayed The power consumption information of 16 appliances was provided by an ECOIS; information on all the electric appliances in a household was not supplied. Power consumption for lighting, which consumes a large portion of the consumption of the whole household, was included in the others category and not displayed di- Daily Power Consumption [kwh] Displayed Not Dis. Before ECOIS Installation Displayed Not Dis. Displayed Not Dis. Displayed Not Dis. Displayed Not Dis. After ECOIS Installation Displayed Not Dis. Displayed Not Dis. Displayed Not Dis. Displayed Not Dis. No.1 No.2 No.3 No.4 No.5 Household No. No.6 No.7 No.8 Ave. Not Dis.: Not Displayed Fig. 17. Power consumption of appliances whose power consumption was/was not displayed.

16 T. Ueno et al. / Applied Energy 83 (26) rectly. However, it is hard to believe that the improvements in energy awareness were effective only with regard to the displayed appliances. It is hoped, therefore, that energy-saving activities such as reducing standby-power of those appliances not displayed, and turning off lights when they are not in use were carried out, despite the fact that they are not displayed. Fig. 17 shows the power consumption of appliances whose power consumption information was and was not displayed by an ECOIS. The total power-consumption of the displayed appliances was reduced by about 12% while that of the not-displayed appliances was reduced by about 5%. The power consumption of not-displayed appliances increased only in household no. 4, whose overall power consumption increased as well. Thus, the installation of an ECOIS had an influence on the energy-saving awareness of the customers. 4. Conclusions In this paper, an on-line energy-consumption information system for motivating energy-saving activities was constructed, and the energy awareness and energy-saving activities induced by this system were described, based on field research. The major findings can be summarized as follows: The responses of residents to the questionnaire generated by the system were received for more than 2 months and provided useful information. The participants became especially interested in the daily-load curve, which is more detailed than the total energy-consumption per day. Comparisons of power consumption before and after installation of an ECOIS revealed that the power consumption of many appliances had been reduced. The average reduction in the power consumption of the whole house as a result of the installation of the system was estimated at 9% over eight households. By the installation of the system, energy-saving activities such as changes in the use of heating appliances were carried out. As a result, power consumption for heating the living room after installation became about 77% of that before installation. However, the amount of increase in city gas and kerosene consumptions for space heating after the installation of an ECOIS was unknown, and it is therefore desirable to display simultaneously not only electric power but also other energy sources such as city gas when supplying energy information. By changing the awareness of consumers, patterns of television use changed and power consumption was consequently reduced. On average, approximately 5% of the power consumption of T.V.s in the living room was reduced for eight households. Refrigeration capabilities were adjusted for two refrigerators and for one freezer, and large reductions in power consumption were achieved. Significant energy-saving effects can therefore be expected by adjusting the capabilities of refrigerators and freezers whose power consumptions are large; this is very easy and not nec-

17 182 T. Ueno et al. / Applied Energy 83 (26) essary to repeat. However, these kinds of activities are not always appropriate since it changes the environment inside the refrigerator/freezer, and this must be taken into account when for example energy-saving tips are propagated. Standby power and power consumption to retain warmth were reduced for many appliances by changing the operation mode at standby or disconnecting the plug. The total power consumption of the appliances displayed on an ECOIS was reduced by about 12% and the total power-consumption of the not-displayed appliances was reduced by about 5%. Thus, it can be conceived that installation of an ECOIS influenced the energy-saving awareness of the customers. Acknowledgements This work was supported by the Research for the Future Program of the Japan Society for the Promotion of Science (JSPS-FRTF9712). The authors sincerely appreciate the cooperation of the Osaka Science and Technology Center, the Kansai Research Institute, Administrative Offices of Kizu City and Seika City, residents of the monitored houses, and the other collaborators and researchers who helped throughout the project. References [1] Matsui M, Matsubayashi N, Ohta I, Nakajima K, Kusakari K. The development of home energymanagement system, chapters 1 and 2. The society of heating, air conditioning and sanitary engineers in Japan II 1999: respectively [in Japanese]. [2] ECHONET CONSORTIUM. Availabe from: [3] Mansouri I, Newborough M. Dynamics of energy use in UK households: end-use monitoring of electric cookers. ECEEE Summer Stud 1999:3 8. [4] Wood G, Newborough M. Dynamic energy-consumption indicators for domestic appliances: environment, behaviour and design. Energ Buildings 23;35(8): [5] Wood G, Newborough M. Design and functionality of prospective energy-consumption displays. In: Proceedings of the 3rd international conference on energy efficiency in domestic appliances and lighting; 23. p [6] Brandon G, Lewis A. Reducing household energy-consumption: a qualitative and quantitative field study. J Exp Psychol 1999;19: [7] Brandon G, Day A. The impact of feedback on domestic energy-consumption. In: Proceedings of the sustainable building conference; p [8] Egan C. Graphical displays and comparative energy information: what do people understand and prefer? ECEEE Summer Stud 1999:2 13. [9] ECCJ. Availabe from: [1] NEXT21. Second-phase report. Osaka Gas 22 [in Japanese] [11] Tsuji K, Saeki O, Suzuhigashi A, Sano F, Ueno T. An end-use energy-demand monitoring project for estimating the potential of energy savings in the residential sector. ACEEE Summer Stud Energ Efficiency Buildings 2;2: [12] Ueno T, Sano F, Saeki O, Tsuji K. Analysis of energy-saving activities induced by information display system in residential houses. In: Proceedings of the 3rd international conference on energy efficiency in domestic appliances and lighting; 23. p

18 T. Ueno et al. / Applied Energy 83 (26) [13] Huenges-Wajer B. Conclusion of task force 1:definition and terminology of standby power. In: Proceedings of the 1st international workshop on standby power. IEA; 1999 [14] Standby power toward a harmonized solution. In: Proceedings of the 3rd international workshop on standby power. IEA/ECCJ; 21 [15] Ueno T, Sano F, Saeki O, Tsuji K. Determination of standby power from the monitored loadduration curves for home appliances. In: Proceedings of the 21 Australasian university powerengineering conference. p