In this paper, an innovative method is introduced to calculate the optimum size of an autonomous hybrid system to determine the lowest levelized energy cost (LEC) and dummy energy (Edummy) generated from the system with the highest reliability index utilizing an Iterative Optimization Technique (IOT). The system includes photovoltaic (PV) panels, wind turbine generators (WTG), diesel generator (DG) and battery storage. An innovative computer program (CP) has been developed based on real time meteorological data of solar radiation, wind speed, ambient temperature and the load demand of one year in 8,760 hours. An accurate methodology for an autonomous site located in the New Valley Governorate of Egypt and many WTG from different manufacturers for obtaining the maximum energy production at the minimum cost of energy provided by the system has been introduced. The CP modifies the penetration ratio of wind and PV in certain increments to meet the demand load. A validation of the CP is carried out by comparing the acquired results with those obtained from the HOMER software and Grey Wolf Optimizer (GWO). Simulation results showed the effectiveness and simplicity of IOT in determining the optimal size of system.