The advantage of hybrid diesel-electric propulsion is well known in terms of fuel consumption, especially for ships with variegated speed profiles or with different propulsion loads. Nowadays several hybrid configurations are available and in the preliminary design phase, the selection of the best configuration among several options could be a time-consuming task. Therefore, in this paper, a methodology is proposed, based on the main propulsion design parameters, to identify the global ship energy efficiency in function of the operational profile, considering both design and off-design conditions. In order to validate the method, a sea trial campaign has been done and the records have been analyzed. The developed tool helps, during the design phase, to choose the optimal propulsion configuration, number, type, and size, of the main engines and generators. The methodology is used to compare two design solutions, a conventional diesel propulsion and a proposed full electric plant using a \u2018father and son\u2019 power generation
