Wind generation is substantially increasing its share in the electricity generation portfolio in many countries. In the case of Spain, it can more than double in the next 4 years, reaching a 20GW level. To become competitive in a liberalized market, wind energy reliability requirements should be guaranteed, so storage systems are being considered to avoid the impact of the lack of adequate winds on the electricity generation process. This paper, assuming different scenarios for the electricity markets and the wind farm operation, analyzes the minimum requirements on energy efficiency of a storage system based on the use of hydrogen as energy vector to become economically competitive for each of those scenarios. Simulation of a wind park with such a buffer system for different operation scenarios shows a direct dependence of the economical profit on the energy efficiency of this hydrogen backup system. A direct conclusion of the study is the necessity for an improvement of the currently available values of the efficiency of the subsystems that compose the hydrogen buffer. These improvements seem to be possible in the short term when attending to the current research efforts. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.