To address the challenge of minimizing fuel oil consumption in maritime transport, in the current paper a developed weather routing tool is employed and expanded to account the effect of a WASP system. The tool has been developed in NTUA and targets the optimization of a vessel’s route planning by minimizing fuel oil consumption by integrating forecasted weather data. Its core feature is a physics-based model (ship model) employed for the calculation of the main engine fuel oil consumption. The enhancement of the tool concerns the expansion of the ship model to integrate the WASP effect by calculating the developed thrust by the wind and consequently the reduced demanded power from the main engine to achieve the same ship speed. The examined ship is a Kamsarmax type bulk-carrier operated by Laskaridis Shipping Co. LTD, while the examined WASP system is a suction type sail developed by Bound4Blue (eSAIL®). A preliminary assessment of the system is presented, outlining its potential gains, reaching up to 27%, for a wide range of wind speed directions. Examining a past voyage fuel savings of approximately 10% are achieved by the WASP system. The effect of route optimization is also enabled resulting in an additional 3% fuel saving.