This paper focuses on the design and efficiency of selected transmissions for wave and tidal devices. A brief assessment of promising technologies shows the potential of hydraulic and mechanic trans-missions. A comparison between mechanic and hydraulic power take-offs highlights their efficien-cies and individual benefits. Examples for hydro-static drive trains for wave energy converters and their characteristics are described. It is shown how force control, energy storage and smoothing as well as high efficiency can be achieved. A wave-to-wire simulation taking into account the efficiency of all installed components is introduced to assess the performance. At last a test rig of a hydrostatic drive train for WEC is described and exemplary results for cylinder efficiency are presented.
