The speed/power performance of a ship is nowadays not only a contractual, but also a statutory requirement. Thus, it is essential to know the true speed/power performance of the ship, as verified by conducting sea trials before the delivery. Presently, relevant guidelines of the International Maritime Organisation (IMO) include two alternatives for the verification of the speed/power performance of a ship in relation to the calculation of a ship’s Energy Efficiency Design Index (EEDI), namely, the ITTC Recommended Procedure 7.5-04-01-01.1 Speed and Power Trials: 2017 and the ISO 15016:2015 procedure, while noting that ITTC recently revised its recommended procedure and the same is underway for the ISO 15016. In this paper, we will re-analyze the sea trial results of a series of tanker sisterships tested under different conditions, by applying the newly updated ITTC procedure to assess the actual speed-power performance of the ships. In particular, the influence of applying alternative methods in analyzing the sea trial results and the effect of environmental conditions on the achieved speed performance are investigated. The results are very important for many stakeholders of the maritime industry, especially for designers in developing new EEDI compliant ships, for shipbuilders and for shipping companies in planning their new buildings and retro-fittings in view of the implementation time frame of EEDI/EEXI.

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