The potential of on-shore wind energy in Spain is assessed using a methodology based on a detailed characterization of the wind resource. To obtain such a characterization, high-resolution simulations of the weather in Spain during 1 year are performed, and the wind statistics thus gathered are used to estimate the electricity-generation potential. The study reports also the evolution with the installed power of the capacity factor, a parameter closely related to the cost of the generated energy, as well as the occupied land, which bears environmental and social acceptance implications. A parametric study is performed to assess the uncertainties in the study associated to the choice of the characteristic wind-turbine farm used; and comparisons are provided with other similar studies. The study indicates that the overall technical potential is approximately 1100 TWh/y; and that about 70 GW of installed wind power could operate with capacity factors in excess of 24%, resulting in an annual electricity generation of approximately 190 TWh/y, or 60% of the electricity consumption in 2008. Copyright © 2010 John Wiley & Sons, Ltd.