“Green Growth” and “Sustainability” are now keywords for industrial growth engines. This research examines the economic, environmental, and technological feasibility of hybrid systems by simulating a system composed of renewable energy, an existing grid system, and a diesel generator on Jeju Island in South Korea. Korea depends heavily on oil imports. Thus, in Korea, efficient energy management is imperative. For this reason, the current Korean administration is striving to improve its energy infrastructure with the construction of stable energy supplies and reliable systems the implementation of energy policies, such as smart grids, and the diffusion of renewable energy generation sources. This study finds that the most economically feasible hybrid system is a grid-connected wind turbine–photovoltaic–battery–converter hybrid system. Given the economic feasibility of this hybrid system, implementing it would decrease the price of electricity in Jeju. Both the implications and limitations of this study will be discussed in the last section of this paper.