The main focus of this paper is to select an economically suitable sustainable standalone power supply system for a remote off-grid town in Western Australia. Existing power systems of such remote towns in Australia have adverse environmental impacts and contribute to global warming due to the utilization of fossil fuels, especially diesel and gas. The possible electricity supply systems for such towns can vary from a diesel/gas generator towards a hybrid system composed of a generator, wind turbine, photovoltaic system, and battery energy storage. In order to limit the cost of the system and to propose the most economically feasible solution, various combinations of supply systems are considered. These systems are analyzed in this paper by the help of HOMER software to determine the optimal architecture and the control strategy of the supply system. This study has used real demand data of the town, as well as the prices of different electrical components in the Australian market. The scenario which yields the minimum cost of energy is defined and suggested. Also, a decision-making based technique is proposed to help the local electricity utility in finding the suitable solution in the case of budget limits on the investment and annual operation and maintenance. Another aim of this analysis is to investigate and illustrate the impact of a small annual load growth on the size of the selected components for the selected power system, as well as the total net present cost and the cost of electricity. A sensitivity analysis is also performed to analyze the impact of uncertainties of some of the parameters in the outcome of the study to obtain the optimized cost of the selected system.