## 1 Introduction  
In the last decade, electrical energy usage has significantly increased owing to the rapid increase in global population and economic activity, which have caused a rapid increase in electricity consumption in residential, commercial, and industrial sectors. To support the growing economy, electricity providers need to raise the power generation from power plants, thereby supplying the constantly increasing demand. However, a large proportion of the current global power generation still relies on energy extracted from fossil fuels, both oil and gas, which add greenhouse gases to the atmosphere and accelerate global warming. This trend also occurs in Thailand, which shifted from being an agricultural nation with a population distributed across the country to an industrialized country. A large percentage of the population is moving into cities or industrial areas for work opportunities. This increases the electrical energy demand, especially in residential and commercial buildings [1, 2]. According to the Energy Policy and Planning Office, belonging to the Ministry of Energy, in 2019 the electrical consumption for the whole country was 189,551 GWh, which implies an increase from the previous year of approximately 4974 GWh (2.62%). In the residential sector, the consumption was approximately 49,202 GWh, which means an increase with respect to the previous year of approximately 3997 GWh (8.12%). When classifying electricity consumption for the whole country by tariff, the apartment type or residential building with large individuals fall under a specific business category [3]. In 2019, electricity consumption in this sector was approximately 6794 GWh or 3.5% of whole country consumption. It also showed the upward trend with 310.62 GWh, or a 3.3% increase compared to 2018. Thus, there is a challenge in terms of energy demand for the country [4]. To combat energy and environmental issues, Thailand's government issued and implemented the Energy Conservation Promotion Act [5]. This act promotes and enforces both newly built and retrofitted buildings to implement newer technologies and take energy aspects into consideration. Thus, it is important to evaluate the compliance of buildings with building energy codes to ensure that the buildings meet the energy standards and are economically feasible for the project's owners to invest in high-efficiency materials, technologies, and equipment. An estimation of energy consumption in a building needs to be correctly performed to assess its characteristics in terms of energy consumption. Models, calibration methods, and verification through simulation of the energy associated with the entire building were reviewed. As a result, we identified a necessity of energy estimation to implement suitable energy-saving measures [6]. In the case of residential buildings, different load curve models were evaluated and analyzed to provide energy models that consider end uses, habits, and behaviors [7]. Energy estimation with better accuracy can also determine the suitable demand side response from the available information with tolerance to estimation error [8]. This estimation methodology to assess the energy consumption in a building has significant benefits in terms of energy efficiency evaluation and potential energy savings [9]. In terms of energy consumption, research from the European Union estimated the energy consumption in residential [10] and non-residential buildings [11]. The results indicate the effectiveness in reducing energy consumption and improving energy efficiency by incentive policies and strict regulations, which can encourage owners to adopt certain technologies or energy-saving measures. Another study in Malaysia confirmed the potential to reduce energy consumption by applying energy-saving measures [12]. Other factors have a significant impact on energy usage patterns and characteristics, such as different types of buildings [13] resulting from the behavior of their occupants and weather conditions resulting from climate change [14].