With the development of the electrical network and the tools used in it such as motors, types of lighting, and the increasing efficiency, and at the same time the high rise in the price and demand for energy, especially in institutions in which energy consumption is very high. We have become in great need in order to preserve that energy, initiate and audit it well in order to obtain a possible value of energy at the lowest cost, , and then identifying the things that need to be replaced or improved This system is designed to save the load of the building while the excess energy will be injected into the network and the building load is mainly provided through the solar cells. However, if the energy produced by the photovoltaic matrix and the battery cannot meet the load the generator will cover the power deficit. In this research, a new improvement method was developed taking into account the maximum availability and minimum cost of system capital for the optimal size of the photovoltaic power generation system to evaluate the effectiveness and accuracy of the proposed optimization method and was compared to the method used in the Homer program.