Three case study for sizing a hybrid system based on renewable energy, using Hybrid Optimization of Multiple Energy Resources (HOMER) program is presented in this paper. The first case study uses: photovoltaic panels (PV panels), battery, converter and electric charge. The second study includes: wind turbine (WT), battery, converter and electric charge. The third case includes: PV panels, WT, battery, converter and electric charge. The simulation results are presented tabulated and graphical for a better visualization of the differences between them. The three cases on the design of a system to supply a 218 W electric load was performed using HOMER software, for the same load and for the same input data (solar and wind). The input data are given for the location Ramnicu Valcea county. A comparative analysis was made, showing the pros and cons of each cases, in order to allow the investor to choose the most convenient design. The optimal design conditions can reduce operating costs. The program is set up in three steps of the computing module: building and energy grid design, operation simulation, and sensitivity analysis with economic factors. The objective of this program is to optimally design a micro energy grid.