Arrays of flexible polymer piezoelectric film cantilevers that mimic grass or leaves is a prospective idea for harvesting wind energy in urban areas, where the use of traditional technologies is problematic due to low wind velocities. Conversion of this idea into an economically attractive technology depends on various factors including the shape and dimensions of individual films to maximize generated power and to minimize associated costs of production, operation, and maintenance. The latter requirement can be satisfied with rectangular films undergoing flutter in ambient air. Flexible piezoelectric films that displace due to low forces and can convert mechanical energy into electrical energy are ideal for this application. The goal of the presented study is to determine the key dimensions of the piezoelectric film to enhance generated power within the wind range characteristic for urban areas from 1.3 to 7.6 m/s. For this purpose, experiments were conducted in a wind tunnel using piezoelectric polymer films of polyvinylidine fluoride with the length, width, and thickness varying in the ranges of 32–150, 16–22, and 40–64 μm, respectively. Voltage and power outputs for individual samples were measured at wind speeds ranging from 0.5 to 16.5 m/s. Results demonstrated that a single film could produce up to 0.74 nW and that the optimal film dimensions are 63 mm × 22 mm × 40 μm (from considered samples) for the wind energy harvesting in urban areas. Further improvement in power production can be expected when using films with reduced thickness, low elastic modulus, and increased length, and by assembling films in arrays.