This research aims to determine if there is a change in the power and torque of a low-power wind turbine when the roughness of its blades is modified by the accumulation of dirt with different grain sizes. The blades’ roughness was simulated using sandpaper on the leading edges, using two different screenings and 3 percentages of a chord (15, 25 and 40%). Calculations and previous measurements of the wind turbine in clean condition were made to have a comparative basis, as well as to determine the working Reynolds numbers, concluding that at all times, it worked with a turbulent flow and laminar boundary layer. A torque meter was coupled to the wind turbine to obtain the required measurements of torque and power delivered. The wind turbine was tested in all configurations in a closed wind tunnel with continuous flow. Finally, it was observed that combining the larger grain size of the roughness with the higher percentage of chord results in less power and less torque in the wind turbine; therefore, both conditions decrease the operating parameters of the low-power wind turbine.