Providing energy to areas isolated from the electricity grid through the use of a smart integrated renewable energy system (SIRES) is proposed in this study for Valparaiso, Chile. The study analyzes the process of identifying the appropriate size of a SIRES considering technical and economic factors. An optimization model proposed in the literature was modified, and a subsequent spatial–temporal analysis of the different variables was conducted. The model comprises locally available renewable energy resources, such as biomass, biogas, wind power, solar photovoltaic, and thermal power. Furthermore, it was used to determine the energy potential of each of the isolated areas, identifying those areas in which the SIRES could be implemented as a sustainable solution. The design simulates the cost of the initial investment and energy generation in the chosen areas. The study also includes the selection of different system components and the use of the general model to determine the optimal combination of energy subsystems for isolated areas with the aim of minimizing the cost of energy generations. Finally, an economic evaluation showed that the use of a SIRES based mainly on solar energy supported by biomass, biogas, and mini-wind power costs approximately three times less than extending the electricity grid network.