Modeling, numerical simulations and cost analysis are conducted for different energy configurations used to power up a factory load in Tunisia. Three configurations are considered: diesel engine generator (DE) only; combined photo-voltaic (PV)/battery storage bank and hybrid DE/PV/battery storage bank. A nonlinear model that depends on solar irradiation and ambient temperature is used to characterize PV panels. Lead-acid batteries are used in the model to store excess energy produced by PV solar system and diesel generator. The depth of discharge (dod) parameter is used to characterize the batteries. The diesel engine, synchronous generator and excitation subsystems are also modeled. The cost of operating different configurations is investigated for three countries: Tunisia, Jordan and Kingdom of Saudi Arabia (KSA); where diesel prices are heavily subsidized. Different countries are chosen to clarify the driver to use renewable energy for power generation in these countries. The drives could be for saving operating costs, for saving the environment, or for saving both. It is found that the best solution for power generation in KSA is DE. However, the hybrid PV/DE/battery bank solution is the best solution in Tunisia and Jordan. The hybrid system requires about 9 years for balancing the total cost of operation compared to the DE solution only.