The ISO 50001 energy management system (EnMS) standard was published in June 2011 and has been widely adopted by organizations from around the world, including Thailand. From 2014–2017, there was a continuous increase in the number of ISO 50001-certified companies in the East Asia and Pacific regions and, more broadly, the world, although this is not consistent with the number of companies that emerged during this period in Thailand. This information shows that the implementation of energy management in some companies may not be sustainable. This research offers a novel method for assessing the quality of energy management in the form of an energy management system sustainability index (EnMS SI) framework, presenting the economic, organizational, energy performance, and environmental aspects of sustainable energy management. Data collection, from a literature review of related research and the EnMS good practices, was implemented in order to select sustainability indicators and further develop a sustainability index for energy management. The analytic hierarchy process (AHP) and weighted arithmetic mean (WAM) were used to establish an EnMS SI. The study results were then assessed and validated using 31 ISO 50001-certified companies in Thailand. Direct interviews and questionnaires were used to obtain responses from energy management representatives. The studied data indicated that an EnMS SI framework can be used in qualitative analyses to effectively determine the sustainability of an EnMS. Significant sustainability indicators, consisting of continuous benefits, top management commitment, and long-term strategic planning, were found. The results also revealed that the EnMS in Thailand has been significantly economically weak. The EnMS SI framework is a tool for assessing energy management sustainability, which allows for the determination of an organization’s actual strengths and weaknesses. The benefits of this framework include the possibility of determining guidelines for correcting and improving the EnMS to achieve sustainability.

In international management, ISO 50001 has been widely applied in organisations across the world, including Thailand. The main objective of this standard is to continuously and sustainably improve the energy performance of the organisation in order to reduce energy consumption and costs, including alleviating environmental climate change impacts. This standard stipulates the measurement of energy performance improvement using energy performance indicators (EnPIs) and the energy baseline (EnB). This study proposes a simplified model of energy performance indicators ( EnPIs), effective for ISO 50001 energy management at organisational level. Appropriate internal benchmarking is proposed for measuring three levels of energy performance, namely organisational, process, and main machine, through energy consumption, intensity, and efficiency. Multiple linear regression was selected to develop energy equations to express the relationship between energy consumption and significantly related variables such as service usage, operating hour, and CDD for business buildings, etc. The proposed EnPIs are applied to measure the energy performance of the case study of business buildings in Thailand complying with ISO 50001. This method can be effectively used to measure changes in the energy performance of the organisation as well as the processes and considered as a comparative alternative to public benchmarking, such as kWh/m2. The findings of this study are considered to be beneficial for every organisation adopting the ISO 50001 system. This proposed method can be effectively used to monitor and measure the organisation’s energy performance towards sustainable energy management. However, it still has certain limitations. In the case of energy consumption models that are related to non-linear related variables, it is necessary to conduct further studies to determine more appropriate EnPIs.