The exploitation of wave energy using arrays of wave energy converters (WEC), which contain a large number of devices, could have significant impact on the wave climate in the nearshore region. This research investigates the impact of WEC arrays at the Westwave demonstration commercial site, which is located on the West coast of Ireland. The methodology involves the determination of an appropriate transmission coefficient (Ct) from a computational fluid dynamic (CFD) model of a numerical wave tank (NWT) simulation using ANSYS CFX and the subsequent implementation of WEC arrays using SWAN (Version 41.01). Within this analysis, the Ct value from the CFD NWT model was used in SWAN to represent WEC arrays which are treated as obstacles. Hence, a nested local wave model at the Westwave site have been developed and validated for the period of December 2015 in order to accommodate the simulation of WEC arrays. Three array configurations, which contain 12 WECs (single row, two row arrays and three row arrays), have been simulated and analysed to estimate the impact to the wave conditions at the nearshore area, while also considering the effect of array configuration on power captured. The results of the analysis suggest there is minor impact on the nearshore wave climate for all the scenarios, where the reduction in wave height and wave power was below 1% at a distance of between 1 and 3 km from the shoreline (at water depths varying from 20 to 60 m). At a distance of 100–300 m from the shoreline (at a water depth of approximately 10 m and below), a decrease in wave height and wave power of 0.1% and 0.2%, respectively, was observed. In addition, the methodology can also be applied to other types of WEC and study areas depending on the purpose of the project.