An unstructured version of SWAN (Simulating WAves Nearshore) is implemented in the Sea of Iroise (western Europe) to assess the wave energy resource at high spatial resolutions in coastal areas. Numerical results are compared with available measurements of the significant wave height and the peak period at nine locations including (1) long-term offshore observations and (2) medium to short-term data acquired during field campaigns. A medium-term evaluation of the wave energy resource for a eight-years period (2004–2011) is performed exhibiting major nearshore energetic patterns off the isles of Ushant and Sein and in the coastal areas of the bay of Audierne, the Crozon Peninsula and the northern coastline. The variability of wave power production is estimated revealing in accordance with numerical modelling conducted over the European shelf seas significant inter-seasonal and inter-annual evolutions of the resource in the Sea of Iroise. These changes appear particularly noticeable during the winter period with opposite situations in the distribution of monthly average wave energy flux. In the perspective of the implementation of wave energy converters devices, the present assessment is finally exploited to investigate the local distributions of wave energy flux against periods and directions in areas of maximum mean wave power.