The tilt angle is a crucial factor for the optimization of solar Photovoltaic panels and solar thermal col-lectors performance. Therefore in this present investigation, a mathematical model is built using MATLAB Program, in order to determine the optimum tilting angle and the solar irradiation falling on a surface facing south in the United Arab Emirates (UAE) for different periods. Furthermore, PVGIS and PVWatts programs are also applied in order to validate the established mathematical model. Simulation results reveal that when using a mono-crystalline module with 5-kWp peak power monthly variation of the tilt angle for all UAE emirates can produce about 15% solar energy higher than horizontal solar panels. However, seasonal and semiannual adjustments could produce nearly 14% more energy if the tilt angle of the solar panels changed at least two times in a year (semiannually). It is worthy to mention that the yearly fixed optimum angle of 23 degrees for UAE gives about 8% energy gain higher than a horizontal solar panel.