The theory of diffusion of innovation is used to study the growth of wind power technology in different states of India. Though the policies of the central government of India encouraged growth of the wind power sectors, individual states had varying policy measures which influenced the rates of diffusion in wind energy in different states. The state level data of cumulative wind power installed capacity is used to obtain the diffusion parameters using a mixed influence diffusion model (Bass model). The diffusion parameters obtained, especially the point of time when an inflection occurs in the diffusion Curve (t*) and the rate of diffusion at the point of inflection (RPI) can be used to rank the different states. As different states have different policies for promotion of wind power, an attempt was also made to calculate a composite policy index based on parameters such as land availability. preferential tariffs, wheeling and banking, Third Party Sales (TPS) and state specific incentives. It is found that there is a correlation between the diffusion parameters and the composite policy index. This methodology can be used to study or even predict diffusion of renewable energy technologies in future. (C) 2008 Elsevier Ltd. All rights reserved.