In the latest years an increasing interest in fuel consumption reduction during the operational life of ships has been recorded. A huge effort and continuous pressure are performed by IMO on this matter, due to the involved environmental issues, both in terms of air pollution and in terms of natural resources shortage concerns.

Beside the regulatory aspect, it is in the owner’s perception of economic advantage to implement as much as possible the several energy saving options that can be introduced in the design phase and in the operational life of a ship. Many promising approaches are on the table and tools based on different methodologies have been recently developed in order to support the decision making process about the most favourable ship condition, from the energy consumption point of view.

An important aspect of ship resistance, in a real condition, is the so called “added resistance” i.e. the increment of calm water resistance due to the ship advancing in a seaway. This is not a negligible term of the total resistance and it is usually estimated as a percentage (15-20%) of the calm water resistance,independently from the actual environmental condition. In the present paper, by means of a computational tool based on strip theory, a numerical investigation is performed on the added resistance and some comments are given on its dependence on the actual sea-state condition.