Abstract: The characteristics and performance of solar cells and hence the solar modules have been evaluated using computer aided Ray Tracing Technique. A computer simulation program using programming language C was developed to generate sun rays of various illuminations and allowing the rays to intercept sequentially with the active regions of the solar cells of a module. The results of the simulation provide us with the I-V characteristic curves of the module for different values of temperature. The series resistance, Fill Factor (FF) and the optical efficiency of the module have been determined with a view to sizing of module in Photovoltaic Power System.