In this work, we present a methodology for the assessment of the economic value of ocean wave energy schemes. Such an assessment is a necessary tool for supporting investment decisions in the development of wave farms and in the development of wave energy converter (WEC) technology. To overcome the lack of operational experience, the methodology presented includes detailed operational simulations which relate the operational costs and the availability of the plant for power production to the characteristics of the device, the location, and the maintenance strategy chosen. The methodology consists of firstly, a productivity and costs assessment which embodies the operational simulations and secondly, a financial calculator which employs discounted cash-flow techniques to produce selected economic indicators. A case study, consisting of one hundred WECs units deployed off the West Coast of Ireland, is presented to exemplify the use of the methodology. The paper also explores how the key inputs to the assessment affect the economic performance of the case study project via a sensitivity analysis.