In this study, a solar-chimney power plant with an inclined collector roof was simulated using CFD. A 3D domain with the RNG k−ε turbulence closure and a DO non-gray radiation model was simulated. The solar load model using the solar ray-tracing algorithm to simulate solar irradiation was employed. A parametric study was carried out to consider the effect of the collector-roof inclination on the fluid flow and the heat transfer of the Manzanares power plant by adjusting the collector outlet height while the collector inlet height is fixed. The results showed an increase in the system performance while the collector roof inclination increased with respect to the limitations. By comparing the effect of increasing the roof inclination to other ways of improving the system performance, such as increasing the chimney height, it can be concluded that in terms of construction and maintenance, it is safer and more suitable to increase other structural parameters, such as the chimney height or collector radius.