76 in a sense, the social wisdom of the ancestors hardly worked. Due to its high economic growth, Vietnam’s final energy demand increased by an average of 4.1% annually between 2006 and 2015, and if this trend continues, Vietnam’s final energy demand is projected to grow by 2.5 times between 2015 and 2035 (Danish Energy Agency, 2017). According to a 2016 Vietnamese household living standard survey, ownership rates of major household appliances were 92% for a color television, 69% for a refrigerator, 35% for a washing machine, 27% for a water heater and 19% for an air conditioner (AC) (GSO of Vietnam, 2018). Compared to the ownership level of 2006, AC ownership increased by a factor of six, whereas those of other electric appliances increased by factors ranging from one to four. If this proliferation continues, energy demand in the country will further increase, leading to greater impacts on the global environment (Sahakian, 2014). Therefore, it is important to find a way to reduce the energy used for ACs and other household electric appliances. Many studies have been conducted on the indoor thermal environment of houses in Southeast Asia, mainly in the field of building environmental engineering (Kubota et al., 2011; Uno et al., 2003). Kubota and Ahmad (2006) and Kubota (2007) examined how residents used ACs or opened windows to cool their living space. Several studies on household energy use have also been conducted in Vietnam (Kim et al., 2000; Le et al., 2009; Le & Yoshino, 2010; Nagasaki et al., 2011; Sawashima & Matsubara, 2017; Le & Pitts, 2019). Kim et al. (2000) measured the indoor thermal environment (temperature and humidity) of traditional housing in Hanoi, but because this study was conducted in the 2000s, a time when ACs were not in widespread use, the impact of AC use was not examined. Le et al. (2009), Le & Yoshino (2010) analyzed questionnaire survey data to investigate the relationship between electronic appliance ownership and energy consumption. Nagasaki et al. (2011) surveyed energy consumption in six houses in Ho Chi Minh City, the largest city in Vietnam, investigating the hours and temperature setting of AC use. Sawashima & Matsubara (2017) surveyed four houses in Haiphong, northern Vietnam, and the hours and temperature setting of AC use. Le & Pitts (2019) studied the energy usage patterns of 60 households in Tuy Hoa City on the south-central coast of Vietnam. Despite these many studies, there are no studies that have focused on AC use by different income groups in Vietnam. Here, we collected basic data on AC use and household energy consumption from households in different socioeconomic classes in urban and rural areas of Vietnam. Using this data, we then considered the following research questions: 1) When and how are electric appliances used in urban and rural areas of Vietnam? 2) How has the spread of electric appliances investigated A. YOSHIDA et al. differed from that in other Asian countries, such as Japan? 3) What are the drivers and barriers to owning new electric appliances, especially cooling appliances such as ACs? 4) To what extent are people aware of energy saving? Vietnam is a large country with a north–south orientation. Vietnam’s climate can be divided into two zones: a tropical monsoon zone and a warm–dry winter zone. The southern part of Vietnam, especially Ho Chi Minh City and the surrounding Mekong Delta, has a tropical savanna climate, with annual average temperature ranging from 22°C to 27°C all year round. The northern part, the temperature typically varies from 14°C to 33°C. We accounted for the two different climates by conducting our interview survey once in northern Vietnam (Hanoi in March) and once in southern Vietnam (Long An Province in August). Both surveys were conducted in 2016. including Hanoi, has four seasons, and Hanoi is the capital of Vietnam and the second most populated municipality. Its population exceeds seven million and the main industry there is the service industry (GSO, 2020). Long An (population 2 million) is a mid-sized province that adjoins Ho Chi Minh City and is located at the entrance to the Mekong Delta. Since 2002 improvements in transportation access have resulted in many factories relocating from Ho Chi Minh City to industrial zones in Long An, which together comprise 28 industrial parks (Runckel, 2006; VOV World, 2016). The major industry in Long An is manufacturing, which accounts for half of the gross regional product, although the production of raw materials in rural areas accounts for approximately 20% of the gross regional product (GSO, 2020). Fifteen households were selected in each region with consideration given to ensuring a selection of households that would represent the diversity in Vietnam with respect to household size, monthly income and occupations of family members. Local officials helped us select households from each income class. Monthly incomes in urban areas of Hanoi and Long An were classified as low, <10 million VND (457 USD; 1 USD = 21,887 VND); middle, 10–30 million VND (457–1,371 USD); and high, >31 million VND (1,416 USD); in rural areas of Hanoi as low, <5 million VND (226 USD); middle 5–10 million VND (226–457 USD); and high, >10 million VND (457 USD) ; and in rural areas of Long An as low, <5 million VND (226 USD) ; middle, 10–25 million VND (457–1,142 USD); and high, >25 million VND (1,142 USD). In Hanoi, nine households were selected from the central districts of Hanoi City (i.e., Ba Dinh District, Dong Da District and Hai Ba Trung District) and the fast-developing new urban district Thanh Xuan; and six 2. Methods 2.1 Survey Area
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