The Roof Top Solar Chimney system is a natural solar updraft technique utilizing the solar energy to generate wind stream within the system passage that has enough driving force to create stack effect. The influence of the inlet shape of the solar air collector on the solar chimney performance was investigated experimentally and numerically in the present paper. Four different inlet configurations have been modeled and ANSYS FLUENT software was used to simulate and visualize the 2-D aero-thermal flow field surrounding the inlet region. Experimental measurements of the four different inlets were conducted using a roof top solar chimney set up to validate the simulation results and to evaluate and compare the system performance at each inlet configuration. The experimental model has two identical transparent covers installed over the roof of a room model, opened at the top to allow air flow from both sides to a chimney pipe. It was found that when the inlet has vertical cross section, it offered the best performance as the velocity and mass flow rate of the air at the chimney was observed to be higher compared with the other three inlet configurations. When the inlet cross section was employed as horizontal, the performance of the collector was reduced by 84 compared to the vertical inlet setting, at 1.00pm. The CFD analysis demonstrated, interestingly, that most of the air flow in the collector was directed from upper region above the inlet, while small amount is flowing from the bottom side of the inlet. This justify the reason of very low performance of air solar collector with horizontal orientation. The results revealed the possibility of reducing the area of the transparent canopy of the solar chimney power plant and convert the outer region to open top absorber. © 2017 Elsevier B.V.