Among the more efficient and sustainable processes that are studied for massive hydrogen production, High Temperature steam Electrolysis seems a promising process. When operating in the autothermal mode, this process does not require a high temperature source for the electrolysis reaction but only a thermal energy source able to supply enough heat to vaporize water. Using a simplified economic model, we assess the impact of the temperature, pressure and thermal energy cost of the heat source on the process competitiveness. Results show that medium temperature thermal energy sources could be coupled to the High Temperature Electrolysis process without resulting in strong overcosts. Besides, key parameters are also identified among the electrolyzer characteristics. Relevant results indicate that R&D on electrolysis cells must continue focusing on the lifespan of these equipments, for which a target lifespan of 3 years could be established. (C) 2010 Elsevier Ltd. All rights reserved.