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FAQs

Environment FAQs

  • Why do some sister ships have different ratings?

    A vessel’s EVDI™ value is based on many parameters and if one of these parameters differ between sister ships they could have a different EVDI™, moving them into a different rating bracket. The base data used in the rating calculation of an individual vessel is provided in RightShip’s Ship Vetting Information System (SVIS™) so the source of differences between sister ships can be checked.


  • If I know how far a vessel is travelling can I work out an exact footprint based on the information in your website?

    EVDI™ is an estimated measure of the CO₂ emitted per tonne nautical mile travelled only and will not produce an exact CO₂ footprint for a particular journey.

    Actual emissions for a voyage will vary from this theoretical calculation, as the fuel consumption and consequent emissions will vary with voyage characteristics such as actual speed, cargo load and weather conditions.


  • How does slow steaming impact the GHG Emissions Rating?

    Slow steaming will not impact a vessel’s EVDI™ and consequently will not impact a vessel’s GHG Emissions Rating. The GHG Emissions Rating is calculated based on a vessel’s design specifications and therefore is not impacted by the way the vessel is operated.

    RightShip affixes a plus (+) sign to a vessel’s GHG Emissions Rating to recognise a retrofit or upgrade.


  • Is a newer vessel more efficient than an older vessel?

    It is a pre-conception that newer is always more efficient. While the technology is available to build a more efficient vessel, this technology is not always applied to every new vessel built.


  • What does it mean if a vessel has a G rating?

    The A – G rating is a measure of relative efficiency and is based on the EVDI™ Size Score. The EVDI™ Size Score is calculated after applying a logarithmic transformation to EVDI™ values of vessels of similar size and type. A vessel with a ‘G’ rating is more than two standard deviations less efficient that the mean score of other vessels of similar size and type.


  • If the EEDI was designed for new vessels, can it be applied to existing ships?

    The Denmark paper that initially proposed the Energy Efficiency Design Index (EEDI) to the International Maritime Organization’s (IMO) Marine Environment Protection Committee (MEPC) stated that “it is not inconceivable that design indices or equivalent may be applied retroactively to existing ships.”

    The IMO have now documented EEDI benchmarks and reference lines based on the existing fleet and historical data.

    RightShip has developed the Existing Vessel Design Index (EVDI™) to address the 60,000+ vessels currently in service, which annually contribute over one billion tonnes of CO₂ into the atmosphere.

    A comprehensive explanation of the application of the EVDI™ to existing ships is accessible here.