The Energy Efficiency Design Index (EEDI) regulation introduced by the Marine Environment Protection Committee (MEPC) within International Maritime Organization (IMO) has the aim to improve new vessel designs in order to reduce the shipping sector CO2 emissions. But the regulation, in its current form, does not effectively assess the ships energy performance. As the Attained EEDI calculation considers only a single operating point (75% main engine power, fully laden condition, calm seas, constant auxiliary engines power) and does not take into account the ship thermal power system, improvements of the ship energy efficiency cannot be assessed realistically. In this paper, a new approach is proposed to more realistically determine the energy efficiency for tankers. The proposed approach represents better the ship entire operating envelope whilst considering the major ship energy consumers. Thus, a better insight in the ship power system performance is provided allowing for the identification of operating points with low operational efficiency. If implemented for regulatory purposes, this approach could yield a higher impact on the tanker’s power plant design leading to the increase of the ship energy efficiency, the reduction of the GHG emissions and the ship environmental footprint improvement
