Abstract Because of the development of wind energy technology, the power coefficient of a wind turbine is close to its theoretical limit. The conversion rate of wind energy that humans can extract from a given wind farm, however, is far from ideal. Increasing the power density by optimizing the arrangement of wind turbines has been a popular field of research in recent years. In the present work, a systematic study on the influence of array configuration on the power performance of vertical axis wind turbines is performed through wind tunnel experiments. Multiple transversal and longitudinal layouts are tested, and both the relative position and rotational direction are considered. The optimal mode of the transversal layout is counterforward rotation, and the maximum power coefficient of the turbine pair is 8.2% higher than that of an isolated turbine when the transverse spacing is 2.4 rotor diameters. The maximum power coefficient of a downstream turbine is found to be increased by 45% and 61.1% with respect to an isolated turbine in the two-turbine and three-turbine longitudinal layouts, respectively. Triangular and truss layouts are proposed based on the prevailing wind direction. The results of the experiment confirmed that further improvement of the average power coefficient can be obtained by optimizing the array configuration of the turbines.