Starting from the observation that an important next stage in exploiting the ocean energy is to install large arrays of several identical devices in order to raise their overall electricity production, the present work has as objective to assess the local and coastal impact of a large wave farm that would operate in the Portuguese coastal environment. The target area is the Portuguese maritime pilot zone, São Pedro de Moel, which is located in the central part of the Portuguese continental nearshore. A generic wave farm was considered and various transmission situations were analyzed. The study started with the situation without wave farm (zero absorption) and subsequently different scenarios were considered by gradually increasing the conditions to the hypothetic case of the total absorption. For each case study, model simulations were performed covering the entire year 2009 using a wave prediction system based on Wave Watch 3, for the wave generation at the level of the entire North Atlantic Ocean, and on SWAN, for the coastal wave transformation. In this way, a comprehensive picture of the possible impact of the wave farm is provided. The results show that the presence of a wave farm operating offshore has a strong influence on the wave conditions immediately down wave. Although this influence is usually attenuated at the level of the coastline, it appears as obvious a general decrease in terms of significant wave height due to the wave farm, but also some other wave parameters are modified.