Electricity consumption propensity of different household members in apartment house

Journal of Chongqing University (English Edition) [ISSN 1671-8224] Vol. 11 No. 1 March 2012 Article ID: 1671-8224(2012)01-0019-07 To cite this article: KIM Yu-lan, SEO Youn-kyu, JEON Gyu-yeob, HONG Won-hwa, KIM Kwang-woo. propensity of different household members at apartment house [J]. J Chongqing Univ: Eng Ed [ISSN 1671-8224], 2012, 11(1): 19-25. propensity of different household members in apartment house KIM Yu-lan 1,, SEO Youn-kyu 1,, JEON Gyu-yeob 2, HONG Won-hwa 1, KIM Kwang-woo 3 1 Kyungpook National University, Daegu 702-701, Republic of Korea 2 Jeju National University, Jeju 690-756, Republic of Korea 3 Seoul National University, Seoul 158-867, Republic of Korea Received 23 October 2011; received in revised form 7 December 2011 Abstract: South Korea is an energy-guzzling country. Economic reasons in the country force its households to save more energy. Household energy consumption in South Korea has grown slow compared to other sectors and household energy consumption per capita is lower than the OECD (Organization for Economic Co-operation and Development) average. However, its per capita electricity use soared and expected to keep climbing mainly due to the increasing number of one-person household. To establish effective strategy against a possible electricity shortage, the amount of electricity energy consumption needs to be understood clearly first. We adopted both general survey and detailed survey for people living in apartment housings and collected data on electrical instrument use according to individual schedule. Based on these data, we tried to analyze electricity consumption patterns resulting from energy using activities at home and find out electricity using tendency according to each family member s characteristics in apartment housings. Keywords: apartment house; electricity consumption; lifestyle; household members CLC number: F407.6 Document code: A 1 Introduction a 1.1 Background and purpose South Korea is a heavy energy user, ranking the world s 10th on the energy guzzling country list in 2008 while its economic size was the 12th in the world. Looking into each sector, the industrial sector used 58.3 of the country s energy consumption; transportation, 19.6 ; residential & commercial, 19.8 ; and public & others 2.2. The residential sector accounts for about 11.6 of the nation s total KIM Yu-lan: yu2530@naver.com. Corresponding author, SEO Youn-kyu: s0913@knu.ac.kr. Funded by the National Research Foundation of Korea (NRF) of the Korea Government (MEST) (No. 2011-0029867). energy use. [1] However, since the sector s economic effect is lower than the industry and transportation sectors, its energy saving is being emphasized. South Korea s energy saving policies has improved the efficiency in its energy use. Building or equipment change and repair are limited since they require high cost, however. Energy consumption is caused by human activities. Thus, governments set up policies mainly to guide people s habitual behaviors to save energy. Energy saving activities will be more effective at home than in the office. Because people have to pay for their energy use at home. South Korea s annual average residential energy use has grown by 1.3 from 1990 to 2008, showing a slower growth compared to other segment growth rate. During the same period, per capita residential energy consumption has risen by 0.6 on average. Per capita residential energy use in South Korea is 0.39 TOE (tonne of oil equivalent), at a similar level to 0.37 TOE in Japan, and lower than 0.88 19

TOE in the US and 0.60 TOE of the OECD (Organization for Economic Cooperation and Development). [2] However, residential electricity use per capita rose rapidly by 5.9 on average annually. Energy saving policies has improved the electricity-use efficiency of electrical appliances. But as such appliances penetrated swiftly and became bigger and more sophisticated, the total residential electricity use has soared. In addition, while the population decreases, rising nuclear families and one-person households are expected to push up energy consumption in the segment. To respond to the situation appropriately and set up effective strategies, we need to understand the facts regarding the energy consumption. Existing studies found that residential electricity use depended upon the size of floor space, income and number of family members of a household. [3-7] Korea lacks studies on energy consumption according to individual lifestyle. We analyzed electricity consumption by considering household member s energy use patterns at home to find out consumption propensity of electricity according to household members characteristics. 1.2 Scope and methods First, the study will look at the energy consumption of residential buildings and its change according to social changes. Among others, to prepare for a continuous power shortage, we will focus on characteristics in residential electricity use and electricity use which has been on the rise every year. Residential buildings are divided into two categories: detached housing and apartment housing. We investigated the apartment-style housing where constructional characteristics of each household are similar. Energy consumption data collected here are about basic energy use excluding those on cooling/heating systems affected by seasonal changes. We employed general surveys and detailed surveys to understand how the energy use varies depending upon apartment housing residents behaviors. Through the general survey, we collected constructional information including floor number and residential size plus home lighting and power consumption of electrical appliances. The detailed survey was utilized to know a resident s lifestyle and energy use patterns by recording each resident s behaviors as well as lighting and electrical devices he/she used every 30 min. Based on the data, lifestyle and power consumption patterns can be analyzed and energy consumption patterns will be more closely looked at by time and by behavior. The study aims to investigate the relationship between behavior and energy consumption to identify electricity use patterns according to household-member characteristics and family composition. 2 Energy consumption in the residential sector and energy consumption behavior 2.1 Energy use in residential buildings Table 1 shows that in 2008, 44.2 of Korean households energy for heating; 23.8 for hot water; and 19.1 for electrical appliances. As for heating, energy basic unit cost has significantly reduced thanks to residential building structure change, improved the performance of insulation and the efficiency of boiler. Moreover, heating energy source shift to natural gas and electricity from coal and petroleum for enhanced energy use efficiency. Table 1 Energy use change in household sector [2] Unit: Type 1990 1995 2000 2005 2008 Average annual growth Heating 66.4 59.9 53.9 47.1 44.2 1.0 Cooling 0.2 0.5 1.1 1.5 2.0 14.1 Hot-water 16.6 20.0 23.1 25.4 23.8 3.4 Cooking 8.0 7.7 8.1 8.1 9.0 2.0 Lighting 0.8 0.8 1.1 1.4 1.7 5.8 Appliance 8.1 11.1 12.7 16.5 19.1 6.3 Total 100.0 100.0 100.0 100.0 100.0 1.3 20 J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25

Table 2 Energy source changes in household sector [2] Unit: Type 1990 1995 2000 2005 2008 Average annual growth Coal 53.8 7.7 3.4 4.8 5.2 11.1 Petroleum 29.6 56.3 42.0 27.2 19.7 1.0 City gas 2.7 19.3 34.4 42.2 45.5 18.5 Electricity 9.1 12.4 14.9 19.4 22.9 6.6 Heat energy 0.4 3.1 4.8 6.0 6.4 18.0 Renewable energy 4.4 1.1 0.5 0.4 0.3 12.6 Total 100.0 100.0 100.0 100.0 100.0 1.3 The high energy use increases in cooling is 14.1, and appliances 6.3, on annual average (Table 1). Energy consumed for cooling is seemed soaring due to heat wave, tropical night phenomenon and urban heat island caused by global warming. Rise in appliance energy use is seemed because of increasing one-person households and home appliances growing ever larger. Almost all home energy use is based on electricity, thus the use of electricity energy source is expected to rise continuously together with its importance in energy source used (Table 2). South Korea s energy use per household is decreased to 0.9 mainly because increasing nuclear families and one-person households cut the number of people per house. But electricity use per household grew by average 4.4 a year, a twofold increase in 2008 compared to the 1990s. It is because the one-person household would still need at least a minimum set of household items and electrical appliances as basic living essentials. 2.2 Residential electricity consumption characteristics The Korea Power Exchange conducted The Survey on Electricity Consumption: Characteristics of Home [8] Appliances to provide policy-building ground materials for residential demand estimation and analysis plus effective energy use management. The study investigates home penetration situation nationwide and residential electricity use patterns to compare them with the past data. It surveys national residential energy users every 2 years with 4 000 sample households for general survey including 500 for detailed survey. The general survey is carried out by surveyors visiting homes and asking and the detailed survey relies on answers from the surveyed for a week. The surveys mainly investigate to find out the kind of appliances, appliance penetration, power use patterns of each appliance, and penetration estimation a household has. Most appliances, in particular TVs, refrigerators for kimchi, air conditioners, and computers, are well penetrated in apartment-style housings rather than detached housings. By energy use, electric pads/blankets and other heating supplement devices were utilized more by 27.5 to record 0.55 device per house in 2009 compared to the situation in 2006. This is largely due to price rises in city gas and petroleum which are heating sources. Home use of electric fans, air conditioners, and other cooling devices is increasing steadily due to the increasing of apartment housings penetration and higher temperatures from global warming. In addition, people use more electric energy at their kitchens as they use more kitchen electric appliances for convenience such as electric rice cookers, microwaves, and electric frying pans. In line with income rise, IT development, and individualization, multi-media gadgets are more used such as netbook, portable media players and smart phones, which will also require more electrical energy. 2.3 Energy consumption behavior According to the Korean Time Use Survey s behavior table, [9-10] people tend to use time mainly for necessary living activities, mandatory activities and leisure activities. Time for each activity is more specifically analyzed but we will focus on residents actions related to energy consumption in the house. Among the time for necessary living activities, we are interested in sleeping, eating/drinking and personal hygiene/dressing/grooming. In mandatory activities, we focus on students homework, household care and family care. In leisure time, people tend to attend freetime courses, enjoy mass media or hobbies and other recreational/leisure activities. To support such activities, they use appliance for lighting, cooking, entertaining, J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25 21

information searching, and cooling/heating. Most residents go out for work during the day and stay at home from the evening to the next morning. Thus, the period of home-stay coincides with lighting period. However, people staying at home during the day still use lights to support their activities. Since apartment-style housings have no window at bathrooms, in particular, people have to use lights in a bathroom. Kitchens also need high brightness, requiring daytime light use as well. [11] 3 Results and discussion 3.1 Outline of survey We surveyed apartment-style housing residents through the general and detailed surveys. Fifty-seven households were examined and the total number of family members surveyed was 187. However, only 169 cases of detailed surveys were possible because it was difficult to interview people under the age of 4 and over 70 or people having irregular work schedules. Table 3 shows the general aspects of the investigation. Among the surveyed, 91.2 lived in apartment houses, 7.0 in row houses, and 1.8 apartment units in a private house. As for the number of household members, 40.4 of them had 4 members; 35.1, 3 members; 15.8, 2 members; 5.3, 5 members, and 3.5 1 person. 73.7 were parents and children households, 10.5 were single parent and children households, and parents-only homes were 5.3. Siblings-only households, one-person household, and 3 generation households were 3.5 respectively. Most of them had more than 2 members and formed with 2 generations: parents and children. In all the household surveyed, those with a floor area between 99.17 m 2 and 132.23 m 2 were 43.9, followed by 28.1 ranging from 66.12 m 2 to 99.17 m 2 and 10.5 ranging from 132.23 m 2 to 165.29 m 2. An average residential area is 111.62 m 2 and the average number of family members is 3.2 persons. This is because nuclear families live in a relatively smaller home in many cases. The detailed survey studied 83 males and 86 females. Thirty-nine people were a husband with an average age of 52.2. Forty-eight people were a wife with an average age of 49.7. There were 23 full-time housewives and 25 housewives had a job. There were 80 children at an average age of 22.5. Among them, 42 are males and 38 are females. Normally, families surveyed under the study had 4 members with father at the early 50s, mother at late 40s and 2 university-student children. They live in a house ranging from 99.17 m 2 to 132.23 m 2. 3.2 Behavior on the electricity energy consumption Most residents used no electric appliances while sleeping. There were rarely people using sleep lights and some used cellular phone chargers. Normally cellular phone battery charging takes 2 h to 3 h but cell phones are still plugged in during sleeping until the next morning, thus consuming electric energy to standby. For personal hygiene, people use bathroom lights. For grooming, they used bathroom and room lights plus hair dryers. Men used hair dryers for 3 min to 5 min and women for 3 min to 15 min more variously. During the leisure time, they mostly watch TV and use computers. Some said they read books. Recreation and leisure requires light use and sometimes supplemental lighting devices. But people tend to turn on TV even though they do something else other than leisure-time activities or do not do something special. No one surveyed attended free-time courses. Students used computers or room lights to study. Apartment-style housings have a separated dining table lighting and people use tables much to have a meal. Since they watch TV during meals, some had meals in the living room if they could not watch TV from the dining table. As to household care, many homes used an electric rice cooker. Lights at kitchen and dining table plus microwave were used to prepare a meal. Refrigerators and water purifiers work 24 h a day. Since these appliances are used anytime, it was hard to measure energy consumed. Therefore, they are excluded from this analysis. 3.3 Electric energy consumption of different household members To find out individual household members electric energy consumption, we excluded 24 h using appliances such as refrigerators and water purifiers. We found that lifestyle varies according to the person s job and influences hours staying at home. The research analyzed lifestyle of each member and his or her electric energy use patterns according to jobs. The husband s average monthly residential electricity usage is 32.00 kwh/month (Table 4). By occupation, office workers used 37.16 kwh/month the most among 22 J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25

the surveyed followed by self-employed workers with 26.64 kwh/month. Transporting business workers used the least amount of electricity among them with 12.03 kwh/month. People involved in the transportation service industry tend to stay at home for the shortest hours among all and they sleep in a lot when they are at home, thus using the least amount of electric appliances. The wife s average monthly residential electricity usage is 61.50 kwh/month (Table 5). Full-time housewives used 85.36 kwh/month and working married women used 46.45 kwh/month. Among the working married women, students used electricity the most with 85.48 kwh/month, which is close to the electric energy used by full-time housewives. Office workers used 43.84 kwh/month followed by selfemployed 31.19 kwh/month. Full-time housewives used 1.8 times more electricity because of more household care activities. However, in this group, students show a similar amount of electric energy consumption to fulltime housewives. The reasons are that they used lights and computers at home a lot to do homework and study and they do lots of household cares during they stay at home which is longer than other occupational group has. Table 3 General aspects of the investigate Type Number Percentage/ Type of housing Apartment house 52 91.2 Row house 4 7.0 Apartment units in a private house 1 1.8 Number of household members 1 Person 2 3.5 2 Persons 9 15.8 3 Persons 20 35.1 4 Persons 23 40.4 5 Persons 3 5.3 Generation in household 3 Generations Grandparents Parents Children 2 3.5 2 Generations Parents Children 42 73.7 Single parent Children 6 10.5 1 Generation Couple 3 5.3 Sibling 2 3.5 1 Person 2 3.5 Size of floor space 33.06 m 2 0 0.0 from 33.06 m 2 to 66.12 m 2 4 7.0 from 66.12 m 2 to 99.17 m 2 16 28.1 from 99.17 m 2 to 132.23 m 2 25 43.9 from 132.23 m 2 to 165.29 m 2 6 10.5 from 165.29 m 2 to 198.35 m 2 3 5.3 198.35 m 2 3 5.3 J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25 23

Table 4 Electric energy consumption by husband s job Type Number Percentage / Consumption/ (kwh/month) Office worker 27 69.2 37.16 Self-employed 9 23.1 26.64 Transportation 3 7.7 12.03 Total 39 100.0 32.00 Table 5 Electric energy consumption by wife s job Type Number Percentage/ Consumption/ (kwh/month) Full-time housewife 23 47.9 85.36 Working Student 4 8.3 85.48 married Office 13 27.1 48.83 women worker Selfemployed 8 16.7 31.19 Sub-total 25 52.1 46.45 Total 48 100.0 61.50 The average monthly electricity usage of children was found to be 31.82 kwh/month (Table 6). Elementary school students used 49.26 kwh/month followed by middle school students 42.91 kwh/month, office workers 35.23 kwh/month, college students 33.22 kwh/month, high school students 26.07 kwh/month, and graduate college students 22.91 kwh/month. It seems that the order follows the length of time spent at home as well. The longer people stay at home, the more energy they may use. Notably, high school students stay at home shorter than graduate students but spend more electric energy. This is because high school students study at home more than graduate students using online lectures or study late at night using lights and computers longer. Looking at overall, office workers work shorter than the self-employed and stay at home longer, using more electric energy. Husbands at the average age of 52.7 used 36.06 kwh/month electricity while children at the average age of 28.1 used 35.23 kwh/month electricity. Office workers showed an behavior pattern of wakeup - personal hygiene - dining - preparing to go to work and come back home - personal hygiene - dining - resting - going to bed in weekdays. On weekends, they usually showed an activity pattern of wakeup - dining - resting - dining - resting - dining - resting - going to bed. To rest or enjoy the leisure time, most of them watch TV or use computers. Therefore, what they do during the rest or leisure time is expected to decide electricity consumption amount dramatically. Table 6 Electric energy consumption by children s job Type Number Percentage/ Office worker 7 8.80 35.23 Graduate 16 29.06 22.91 student College 38 33.22 33.22 High school 9 11.30 26.07 Middle 7 8.80 42.91 school Elementary 2 2.50 49.26 school Kindergarten 1 1.30 39.18 Total 80 100.00 31.82 Consumption/ (kwh/month) Working married women used 48.83 kwh/month electricity, which is more than working husbands with 35.4 and working children with 38.6. During the weekdays, they tend to show an behavior pattern of wakeup - personal hygiene - dining - preparation to go to work and come back home - cooking - dining - cleaning table and washing dishes - resting - personal hygiene sleeping. On weekends, they tend to show a pattern of wakeup - personal hygiene - cooking - dining - cleaning table and washing dishes - resting - household care (laundering) - cooking - dining - cleaning table and washing dishes - resting - household care (cleaning) - cooking - dining - cleaning table and washing dishes - cleaning - resting sleeping. Working married women did household cares (cooking) more than other family members. They especially did house cares (laundering and cleaning) at once during weekends. In South Korea, women mostly take care of household cares, thus both full-time housewives and working married women use a significant amount of electric energy consumption. 4 Conclusion We compared electric energy consumption amount of apartment-style housing residents according to their energy consumption behavior. We also looked at electricity consumption propensity of each household member s characteristics. To identify any difference in electric energy consumption caused by a resident s 24 J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25

lifestyle, we collected data on residents lifestyle and energy use patterns through the detailed study which recorded each household member s activities and accompanied light and electrical equipment use every 30 min. By analyzing the data statistically, we compared electric energy consumption between each household members and got findings as follows. Occupation which influences one s lifestyle makes difference in a person s hours spent at home. The longer a person stays at home, the more energy they tend to use. Both working married men and working married women respectively used 35.4 and 56.6 more average monthly electricity usage than the selfemployed. Full-time housewives used 1.8 times more electricity consumption than working married women. Among the working married women, students used electric energy the most with 85.48 kwh/month, which is close to the electric energy used by full-time housewives. As to average monthly electricity usage of each household members, husbands used 32.00 kwh/month electricity, wives 65.10 kwh/month, and children 32.82 kwh/month. Wives used 2.03 times more average monthly electricity usage than husbands and 1.98 times more than children. In South Korea, women do most of the household cares so they use more electricity than other household members. The study is at the basic level for energy demand estimation by analyzing electricity use patterns depending upon residents lifestyle. We compared overall monthly electric energy consumption in consideration of household members characteristics. The lack of samples limited us to study each individual lifestyle further. But following researches may carry out more investigation in this direction with more samples to analyze each member s energy consumption in depth. References [1] Korean Statistical Information Service, Korea Energy Economics Institute. Energy statistics 2008: final energy consumption by sector [EB/OL]. 2009 [cited 2012-04-26]. http://www.kosis.kr/abroad/abroad_01lis t.jsp?parentid=g. (In Korean). [2] Lee SK. Estimate of end-use energy consumption in residential sector, Research Publication N. 2010-05 [R]. EuWang-si (KyungGi-do): Korea Energy Economics Institute, 2010. (In Korean). [3] Seo YK, Kim JY, Jeon GY, et al. A study on the development of electrical load-profile model for apartment through the electrical energy consumption in summer [C]. In: KIAEBS 2011 Spring Annual Conference, Kyungwon University, KyoungGi-do, March 25, 2011. [S. l.]: Korean Institute of Architectural Sustainable Environment and Building Systems, 2011: 205-208. [4] Seo YK, Kim JY, Hong WH. An analysis on the characteristics of energy and water consumption in urban rental apartment [J]. Journal of the Korean Housing Association, 2009, 20(6): 39-46. [5] Cho SH, Jung SJ. A study on the energy-lifestyle of apartment residents [J]. Journal of the Korea Institute of Ecological Architecture and Environment, 2011, 11(3): 19-30. [6] Christoph W, Adriaan P. Modeling lifestyle effects on energy demand and related emissions [J]. Journal of Energy Policy, 2000, 28(8): 549-566. [7] Im KU, Yoon JH, Shin UC, et al. An analysis of electricity consumption profile based on measurement data I High-rise apartment Complex [C]. In: KSES 2011 Spring Annual Conference, EXCO, Daegu, April 7, 2011. [S. l.]: Korean Solar Energy Society, 2011: 127-132. [8] Korea Power Exchange. Survey on electricity consumption: characteristics of home appliances [R]. Gangnam-gu (Soeul): Korea Power Exchange, 2009 Dec. (In Korean). [9] Korean Statistical Information Service. Korean time use survey paper 2009 [DB/OL]. [cited 2010-03-30]. http://www.kostat.go.kr/portal/korea.kor_nw/2/6/4/inde x.board?bmode=read&aseq=70284. (In Korean). [10] Korean Statistical Information Service. Behavior classification of Korean time use survey 2009 [EB/OL]. [cited 2009-09-02]. http://kostat.go.kr/survey/lifestyle/l s_dl/1/1/index.board?bmode=read&bseq=&aseq=157 762&pageNo=1&rowNum=10&navCount=10&currPg =&starget=title&stxt=. (In Korean). [11] Hwang MK, Shin HM. An analysis of day lighting in each space of apartment houses [J]. Journal of the Korea Institute of Ecological Architecture and Environment [ISSN 1598-3730], 2008, 8(4): 43-48. Edited by XUE Jing-yuan J. Chongqing Univ. Eng. Ed. [ISSN 1671-8224], 2012, 11(1): 19-25 25