Photovoltaic (PV) model is used in a simulation study to validate the system design of a PV system. This paper presents a step-by-step (detailed modeling) procedure for the simulation of photovoltaic modules with numerical values, using Matlab/Simulink software package. The proposed model is developed based on the mathematical model of the PV module, which is based on that of an elementary PV solar cell employing One-diode equivalent circuit. A particular Polycrystalline PV module is selected for the analysis of the developed model. The essential parameters required for modeling the system are taken from datasheets. The output current and power characteristic curves highly depend on some climatic factors such as solar radiation and temperature, are obtained by simulation for the selected module with the output power of 250 W and discussed.