Power augmentation features have been proven as one of the wind turbine performance enhancement methods particularly for vertical axis wind turbines (VAWTs). Researches showed that with the aid of a deflector, shroud or a single plate, the power output of a VAWT can be increased remarkably. In this paper, lab tests and simulations were performed to investigate the aerodynamic effects and the flow field around a flat plate deflector as a power augmentation device which is placed at the lower upstream of a micro H-rotor VAWT. From the study, the deflector is able to induce a high velocity wind at the near-wake region which was about 25% higher compared to the oncoming wind velocity. The deflected wind flows improve the performance significantly as well as reduce the self-start velocity of the turbine. Nonetheless, it is highly dependent on the positioning of the flat plate deflector. Both experiment and simulation showed a notable observation on the position effect of the flat plate deflector. From the lab test, with the deflector at the optimal position, the maximum coefficient of power (C-p) achieved was 7.4% increment compared to the bare turbine. Also, from the simulation, the optimal position showed an improvement of averaged C-p up to 33% compared to the bare turbine. The flat plate deflector is simple, low cost, and can be easily retrofitted to existing stand-alone VAWT systems to improve the efficiency making them suitable for on-site power generation in urban and isolated places.