The Photovoltaic simulation tool is important in predicting the energy production of the solar system. This paper presents stand-alone photovoltaic (SAPV) system assessment using PVSYST software. The study used simulation software to develop the reliable SAPV system as well as predicting the yearly energy output. The simulation of the SAPV system configuration is presented using the PVSYST tools software. The total amount of electrical energy generated by PV array that supplied to the load and the various types of power losses are determined. The result obtained the optimal size of SAPV system configuration. Besides, the total energy flow through the whole system is calculated. With PVSYST software, the predicting energy supplied to the load for the whole year can be determined.