A wind/hydrogen demonstration project located at the island of Utsira, ca. 20 km off the west coast of Haugesund in Norway, was officially launched by Hydro, now StatoilHydro, and Enercon in July 2004. The realization of the project came after several years with concept development, system design, and project planning undertaken by several partners. A set of hydrogen energy models (HYDROGEMS) developed at IFE was used in the early concept development and subsequent system design phases. The autonomous wind/hydrogen energy system at Utsira, the first of its kind in the world, was designed to meet the entire energy demand for 10 households using wind energy only, either directly or indirectly via hydrogen. A 600 kW wind turbine is dedicated to the demonstration. The hydrogen system consists of a 10 Nm3/h alkaline electrolyzer (12 bar), a hydrogen compressor, a 2400 Nm3 hydrogen gas storage (200 bar), a 55 kW hydrogen engine, and a 10 kW PEM fuel cell. This gives 2-3 days of full energy autonomy for 10 households. Over the past 3 years a significant amount of operational experience and data has been collected from the system at Utsira. The main objective with this study is to evaluate the technical concept demonstrated, both with respect to system design and operation. The method chosen is to use actual operational data to validate a set of wind/hydrogen energy system modeling tools using HYDROGEMS and TRNSYS. Finally, calibrated system models are used in system simulations to identify improved system designs and control regimes.