Small size wind turbines can be attractive from many points of view: the environmental impact is low, they do not cause instabilities in the power network distribution and they do not need large power storage capabilities. Nevertheless, the exploitation of small turbines usually faces with several shortcomings and the actual return is often lower than expected, mainly because the power curve given by the manufacturer usually does not reproduce the actual behaviour of the turbines during the operating conditions. Using high-resolution wind speed and energy production measurements, this paper presents an in situ experimental analysis of two small size wind turbines with the same rated power, placed in the same urban environment and realized with vertical and horizontal axis, respectively. Wind conditions are particularly interesting as they are characterized by two distinct regimes, corresponding to low (wind blowing from the sea) and high turbulence (wind blowing from the land). The detected power production is discussed, showing the mutual strengths and weaknesses of the two technologies, focusing on the role of the technical features and control apparatus on the one hand and of the incoming wind conditions and turbulence on the other. (C) 2015 Elsevier Ltd. All rights reserved.