Remote areas in the Indonesia archipelago are mostly isolated from the utility grid and powered by expensively known diesel generators. Due to the limited access and transportation system, the diesel fuel price can be very high. Therefore, the power can only be served to 1.83% of the population, and worse, these customers are not even fully electrified in 24-hours. This research presents Hybrid Renewable Energy System (HRES) design in the isolated grids in Indonesia. The HRES consists of the existing diesel generators with the solar PV system and Battery Energy Storage System (BESS). The optimized design of HRES is obtained following two objectives, such as the lowest generation cost and highest number of customers served. The HRES is implemented in one isolated grid in Indonesia, and the design is validated using HOMER software. The result shows that the implementation of HRES can reduce the generation cost by 50% and increase the electrification to 7.6%.