# A Regret-Enhanced DEA Approach to Mapping Renewable Energy Efficiency in Asia's Growth Economies
## 3 Results  
Investing in renewable energy projects is seen as the main solution to the problem of sustainable development worldwide. However, each region and each country have their own policies and development conditions. This leads to differences in efficiency of RE investments across countries. The economies of South and Southeast Asia are among the fastest growing economies in the world, in which security and sustainable development of energy are important conditions to ensure stability in economic growth. Therefore, this study aims to evaluate the efficiency of RE investments in South and Southeast Asia by applying the proposed framework, which was mentioned in Section 2. According to the proposed framework, this study considers sixteen countries in South Asia (SA) and Southeast Asia (SEA), which are shown in Table 1, as DMUs of DEA models. Because RE investment data for Singapore and Brunei Darussalam were not found, this study cannot view these two countries as DMUs. The choice of input and output indicators for evaluating RE investment efficiency has been guided by prior empirical studies applying DEA in the energy and sustainability contexts. As inputs, public flows to renewable energy (financial investment), energy intensity (efficiency of energy use), and transmission loss (infrastructure quality) have been widely used to capture the key cost and performance factors associated with energy systems. These indicators have been employed in prior DEA studies such as by [PERSON] et al. (2023) [61], [PERSON] and [PERSON] (2017) [62], and [PERSON] et al. (2022) [63], which assess technical and environmental efficiency in national energy sectors. On the output side, commonly used performance indicators include renewable energy supply, consumption, electricity generation percentage, installed renewable capacity, and non-renewable emissions avoided--all of which reflect the effectiveness and impact of renewable energy investments. These indicators are consistent with studies such as [PERSON] et al. (2015) [31], [PERSON] et al. (2011) [64], and [PERSON] at al. (2025) [65], which  
Figure 3: The proposed evaluation framework using RRUCE model. emphasize output-driven measures of sustainability in DEA applications. The selected indicators and their units are summarized in Table 2.  
For inputs, this study considers the public flows to renewable energy (million 2020 USD), the energy intensity (MJ per 2017 USD PPP), and transmission loss (million kWh). The public flows to renewable energy represent the amount of financial support, investment, or funding provided by government agencies or public institutions to promote and develop renewable energy projects. Public flows to renewable energy are crucial for advancing the adoption of clean and sustainable energy sources such as wind, solar, hydroelectric, and geothermal power. These funds can be used for research and development, subsidies, grants, or direct investments in renewable energy infrastructure and technologies. Energy intensity is a measure of the energy efficiency of an economy or a specific process. The use of purchasing power parity-adjusted dollars accounts for differences in price levels between countries, allowing for a more accurate comparison of energy efficiency across different regions. Lower energy intensity indicates a more energy-efficient economy, meaning that less energy is needed to generate a given level of economic activity. The transmission loss is a measure of the electrical energy lost as it travels through power transmission and distribution systems. These losses occur due to factors such as resistance in power lines and transformers, which convert high-voltage electricity to lower-voltage electricity for distribution to homes and businesses. The losses are primarily in the form of heat and are an inherent part of the electricity distribution process. Reducing transmission losses is essential for improving the overall efficiency of an electrical grid and ensuring that a