Supply development is a major challenge in electric power industry. In order to fulfill this need, and regarding complexities in the energy sector, a comprehensive model such as system dynamics is zimperative. The purpose of this study is to reach this model. The performance of the model was based on the selection of a technology which could give way to the lowest total cost of generation and supply of an electric power unit, thus satisfying energy demand. A time span of 40 years was determined so that all changes and real system dynamics could expose itself. Results show that the yearly trends of electricity demand and supply, on the one hand, and yearly generated electric energy, on the other, are quite comparable.