Optimal sizing and economic assessment are critical aspects of system design in a hybrid renewable energy system. This study objective is to determine the optimal configuration of photovoltaic, wind, and battery system integrated to existing diesel power generators in order to ensure the quality and reliability of electricity production in a remote region. Tuapejat in Mentawai island was chosen as a case study that fit the criteria of isolated grid system. HOMER Pro software is used to conduct simulation and optimization of hybrid renewable energy system in Tuapejat with multiple configuration options. Simulation results showed that a combination of PV-diesel is more optimum compared to PV-wind-diesel and wind-diesel system. The COE and NPC of hybrid PV-diesel are 0.21 cents USD/kWh and 36.0 million USD respectively. PV-diesel hybrid could also reduce fuel consumption by 227 thousand liter per year. The results of the proposed system clearly validated that the system will be able to meet the electricity load requirement throughout the year without any power interruption.