The installed wind power capacity in Spain has grown strongly in recent years. In 2007, wind parks supplied already 10% of the 260 TWh generated electricity. Along that year the installed wind capacity grew by 33.2%, from 11.63 GW ill January to 15.5 GW in December. Wind is nowadays the primer renewable power source in Spain, while the public perception of renewables in general is very positive. The issue of the integration of wind power as a fluctuating source into the power grid is gaining priority. The study we present in this paper has the objective to show that a relatively high share of wind power in Spain can be assimilated by the grid despite the fluctuating character of this energy and despite the fluctuating demand, and without affecting negatively the economy of the power supply systems and of wind firms. (C) 2009 Elsevier Ltd. All rights reserved.