Time at bunkering port if any: If the ship needs to call at a bunkering port to take advantage of cheap- er bunkers, then the deviation must be calculated and included in the voyage duration, in terms of both distance and time lost during the bunkering operation. Charges and fees incurred at the bunkering port should also be estimated and included in the calculation. Bunker costs: The calculation for bunker costs is based on the estimated consumption for the voyage and port time. The bunker cost estimate will take into account the fact that the vessel may load bunkers at a convenient time and place during the voyage, depending on the bunkers remaining on board at the commencement of the ballast voyage and at the availability of bunkers at low prices at the ports of call or at ports with minimum deviation from the intended trip. Safety margins, bunker quality, and type/ grade of bunkers are important parameters, particularly with the advent of Sulphur Emission Control Areas (SECA) and the requirement by authorities and charterers for the vessel to use bunkers of specific grade.