Using generic defined wave energy converters, sub-system block diagrams and reliability diagrams are developed. Devices have common aspects such as moorings or seabed fixings, but the method of electrical power conversion can differ depending upon the device. Reliability analysis is applied to the different electrical power take off mechanisms employed, in particular hydraulic, direct drive and turbine based generation systems. Both a qualitative and quantitative analysis is performed using surrogate reliability data in order to compare the different systems. Critical components are identified and the failure modes analysed in order to provide guidance to improve component design.