Inspection and maintenance costs are significant contributors to the cost of energy for wave energy converters. Maintenance can be performed after failure (corrective) or before a breakdown (preventive) occurs. Furthermore, helicopter and boat can be used to transport equipment and personnel to the device for operation and maintenance actions. This article focusses on a risk-based inspection and maintenance planning approach involving minimization of the overall repair costs including costs due to lost electricity production. The study includes real weather data and damage accumulation as well as uncertainties related with imperfect weather forecasts, costs, structural damage accumulation, inspection accuracy and the applied maintenance strategies. This article contains a case study where the risk-based maintenance strategy is applied for the Wavestar device.