The field of wind energy has made significant progress, yet there is always room for improving the efficiency and the energy extracted from horizontal axis wind turbines HAWTs . There is interest in new renewable energy, including wind energy. This study aims to investigate the effect of trailing edge flap on the performance of the turbine at different numbers of blades, different blade angles, and flap angles. Therefore, an experimental setup includes a model of wind turbine was constructed. The performance of a HAWT model with trailing edge flaps added is examined in this research using the findings of wind tunnel tests. A model with two, three, and six-bladed rotors with a diameter of 260 mm was employed for the wind tunnel tests. The wind turbine model is tested at various blade angles and wind speeds. The model was initially tested at various blade angles without any flaps, β of 10o, 15o and 20o, with two, three, and six-bladed rotors and secondly the wind turbine model was tested with trailing edge flaps with flap angle, α, of 40o, 50o and 60o. It was found that the use of trailing edge flaps can improve the HAWT performance. It was found that 50o is the best trailing edge flap angle, in the current investigation. An improvement of about 55% is achieved when three-bladed rotor is utilized compared to the reference case's maximum power coefficient, which was measured without any flaps and 24.6% improvement in the maximum power coefficient with a six-bladed rotor.