Greenhouse gas (GHG) emissions, which are produced through the combustion of fossil fuels, cause climate change. Unfortunately, South Korea is highly dependent on fossil fuels because of its industrial nature. However, many islands in South Korea have the potential to generate a considerable amount of renewable energy, which should be studied. KEPCO (Korea Electricity Power Corporation), which runs micro-grid facilities in Gasado Island in Jindo, South Korea, built micro-grid facilities in Mozambique in 2015. The micro-grid construction of Gasado Island is considered one of the most successful micro-grid projects of KEPCO, so KEPCO is hoping to expand energy development overseas and become a top-tier global power company. This study aims to find a more technologically and economically optimal hybrid energy system for Gasado Island that KEPCO should have built. We also compared this optimal solution to the Korean government plan. The Korean government plan is the same as the KEPCO plan because KEPCO is classified as a market-oriented public corporation under the Act on the Management of Public Institutions. In the final section of this paper, both the implications and limitations are discussed in detail.