The GHG Emissions Rating aims to increase transparency in the maritime industry by rating ships according to their efficiency, enabling users to make more informed decisions towards a more sustainable future.

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Unabated, shipping’s contribution to GHG emissions globally is projected to increase by an astounding 50% – 250% by 2050. In order to meet the long-term goals of limiting global warming to well below 2°C as outlined in the Paris Agreement, the substantial contribution of shipping to the world’s GHG emissions will need to be significantly reduced. RightShip’s GHG Emissions Rating offers a strategic market mechanism to lift the standard and efficiency of vessels worldwide.


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RightShip’s GHG Emissions Rating was developed in response to the growing trend of global CO2 emissions and customer demand. It offers a systematic and transparent means of comparing the relative efficiency of the world’s shipping fleet.

The GHG Rating compares a ship’s theoretical CO2 emissions relative to peer vessels of a similar size and type using an easy to interpret A – G scale.


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  • Increases transparency in the shipping industry by ranking ships according to their energy efficiency and GHG emissions.
  • Assists the maritime industry to transition to a low carbon economy through informed selection of more efficient ships.
  • Provides the ability to benchmark and track emissions per journey and over time, which can aid the development of a baseline of emissions and an overall carbon-emissions target.
  • Charterers can identify more efficient vessels and reduce their bunker bills.
  • Shipowners can benchmark their vessels against peer vessels to demonstrate the benefits of investing in efficiency.
  • Financial institutions can reduce their risk by investing in efficient vessels ensuring a greater return on investment over the life of the asset.
  • Ports can reward efficient vessels through port incentive programs – reducing CO2 emissions and other criteria pollutants in port, and for the vessel’s entire journey.


The Rating is increasingly being used by charterers, shipowners, financial institutions, and is also gaining momentum as an evaluation tool in various port incentive programs.

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As of early 2018, 85 organisations use the GHG Rating, including:

  • 24 shipowners and managers who utilise the GHG rating to demonstrate the benefits of investing in efficiency.
  • 52 charterers representing 20% of global trade who factor energy efficiency into their vessel selection through RightShip’s GHG Rating. This accounts for 2.4 billion tonnes of cargo or approximately 31,500 annual vessel movements.
  • 4 banks and insurers, 2 ports and 3 terminals also use the GHG Rating in their business processes and these numbers are growing.


The GHG Rating is publicly accessible via, or the enhanced version is available to customers via our vetting platform RightShip Qi.

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Access to Qi allows users to compare a ship’s environmental performance with other vessel data and fleet lists, as well as providing more background information and reporting tools.


A vessel's GHG Rating is presented using the standard European energy efficiency scale. The relative performance of a vessel is rated from A through to G, the most efficient being A, the least efficient being G.


Rather than adopting a ‘one size fits all’ approach, the GHG Rating provides comparison of a peer group of vessels, for example comparing a 100,000 DWT bulk carrier to a bulk carrier of a similar size and type.

Ship types for comparison align with the IMO’s documentation and guidance.

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Categories include bulk carriers, chemical tankers, container ships, crude & product tankers, cruise passenger and general cargo ships, LNG tankers, LPG tankers, refrigerated cargo ships and ro-ro cargo ships.

In terms of sizes for comparison vessels are compared to other vessels plus or minus 10% of their DWT.


The core measure for comparing the relative efficiency of the world’s fleet is grams of CO2 per tonne nautical mile.

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RightShip utilise one of two sources when determining an individual vessel’s efficiency:

  • EEDI (Energy Efficiency Design Index) – measures the theoretical COemission performance of new ships over 400 gross tonnes and is calculated from ship design and engine performance data. This is a regulatory requirement for new ships developed by the IMO (and applied on an ad-hoc basis to existing vessels).
  • EVDI (Existing Vessel Design Index) – developed by RightShip, this index also measures a ship’s theoretical CO2 emissions per nautical mile travelled. However, the EVDI can be applied to existing vessels as well as new builds (where EEDI is not available/applicable).

As the two methods compare relative efficiency on the same basis, a like-for-like comparison of efficiency is achievable – as outlined in DNV GL’s review of RightShip’s methodology in 2015.

EVDI Formula

While the GHG Rating is relatively easy to interpret, the methodology used to calculate the GHG Rating is complex. The EVDI formula is as below:

Source: Based on the IMOs Resolution MEPC.245(66), adopted on 4 April 2014.


The GHG Rating compares the relative efficiency of a ship using the EVDI (or EEDI is applicable).

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The peer group comparison is based on the number of standard deviations a vessel’s EVDI varies from the average for similar sized vessels of the same ship type.

In general, the distribution of the size group fit the following fixed percentiles of the data set.

GHG Emissions Rating Key – Normal Peer Distribution


The bell curve below illustrates the percentage distribution with the corresponding letter displayed in the coloured area under the curve.

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The x-axis is expressed as a count of standard deviations which matches the Size Score in the key.


For example, a 176,382 deadweight tonne bulk carrier has a GHG Rating of D, with a size score of -0.345.

It is considered alongside ships of plus or minus 10% of its deadweight, and is therefore compared to vessels within the range of 158,744 to 194,020 deadweight tonne.

In this case, as there are 1,060 ships in the peer group, approximately 735 are more efficient and 325 are less efficient than this particular vessel.

GHG Emissions Rating – Normal Peer Distribution

Example Bulk Carrier Rating


In January 2015 DNV GL commenced an independent methodology review of RightShip’s GHG Rating.

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The review was finalised in November 2015 and the key points included:

  • There is a trend for the number of A-rated vessels to increase with younger vessel age. This observation (that there seems to be a correlation between year of build and GHG rating, and not only DWT) further strengthens the case for the robustness for the scheme.
  • By analysing a sample dataset of over 10,000 bulk carriers, it was observed that the median difference of EVDI to EEDI was 5% (thereby EVDI being more conservative), which is enough to give an average improvement of A-G rating by over 1 rate, i.e. more than one A-G letter.
  • There exists an incentive for interested parties (e.g. ship owners / managers) to update (‘verify’) EVDI values to remove any uncertainty that may exist between ‘verified’ and ‘non-verified’ ratings.

The executive summary of the outcomes of DNV GL’s methodology review can be found here.


Tidal provides subscribers with updates from RightShip and relating to environmental sustainability. Tidal newsletters are sent out every few months.


The data used to calculate a vessel’s GHG Emissions Rating can be viewed:

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  • In RightShip Qi – for RightShip customers
  • By sending an e-mail to the environment team who will assist you with GHG Ratings and the vessel verification process.
  • Via the Shipping Efficiency website which provides access to the GHG Rating free of charge. A username and password can be set up to gain access.

Source data for the GHG Rating

RightShip recognises that the reliability of its calculations directly correlates to the accuracy of source data. RightShip continues to work closely with ship owners, managers, yards and classification societies to validate the data used for the calculations.

The data utilised for the GHG Rating calculation is, as far as practicable, in line with the IMO guidelines (MEPC.245(66)) for EEDI calculation. RightShip obtains data for the GHG Rating from various industry sources as outlined below.

The source data for the GHG Rating is based on the hierarchy found in the table below.

As outlined in the DNV GL review, due to the pre-defined set of data assumptions applied to ‘non-verified’ vessels, there is an incentive for shipowners to update relevant data within Qi as it is likely to result in an improved GHG Rating.

Most preferred / highest level of verification
Energy Efficiency Design IndexClassification Societies e.g. EEDI Technical Files

EEDI certificate (including supplement)
Ship specific specificationsShip-sourced data, e.g. sea trial and shop test supplied by the vessel owner / manager
Industry / third party data sourcesEngine manufacturer's specifications

Data sourced from ship yards
Least preferred / benefit from verification
IHS Maritime database

Industry publications
IMO publications

IHS Maritime Database


The following documentation is requested to ensure the ship particulars are up to date:

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  • EEDI Technical File – as defined in the IMO Guidelines (MEPC.245(66)) for EEDI calculation.

If the EEDI Technical File is not available, please provide the documentation outlined in the table below.

Upon receipt of the documentation, RightShip’s sustainability team will review and update the vessel particulars and provide the updated GHG Rating.

Sea TrialVref Speed (Knots)Trial Speed at Summer/ Scantling Load Draught at 75% Maximum Continuous Rating (MCR). In the form of a sea trial curve (calculated and/or model curves are acceptable)
Shop Test - Main and Auxiliary EnginesNumber of Engines

Power of engines (MCR)

Specific Fuel Consumption (SFC)

Fuel Type (test conditions)
SFC for the Main Engine is read at 75% MCR

SFC for the Auxiliary Engines is read at 50% MCR
Class Certificate and/or Ship Capacity PlanCapacityDeadweight (DWT)

Gross Tonnage

TEU (if applicable)

CBM (if applicable)
Ship classification notationsCommon Structural Rules (include LBP and LWT)


Shuttle tankers

Cubic-capacity correction factor

General cargo equipped with cranes
Other documentation as appropriateInnovative energy efficient technologies Examples include waste heat recovery and shaft motor generator


As stated above, SFC figures are sourced from vessel-specific shop tests or EEDI technical files.

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If the data is not provided by the ship owner, the values used in the calculation are based on the same assumptions used in the IMO GHG Study and / or detailed in IMO Circulars on the calculation of the energy efficiency measure as listed below.

Main Engine Assumptions (SFCME)
Pre 1983> 15,000205
5,000 to 15,000215
< 5,000225
5,000 to 15,000195
< 5,000205
5,000 to 15,000185
< 5,000195
Post 2008>15,000175
5,000 to 15,000185
< 5,000195
Auxiliary Engine Assumptions (SFCAE)
> 800 kW220
< 800 kW230


If you would like to improve the GHG Rating of your vessel, and have had your vessel verified by RightShip, we suggest you seek advice from a suitable third party. This could include a Class Society, engine manufacturer or technology provider to advise of any energy efficiency measures that may improve your vessel’s rating.

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In advance of planned vessel upgrades you may like to contact to discuss the potential improvements in GHG Rating. Some examples of voluntary energy efficiency measures or upgrades that may lead to a GHG Rating improvement include:

  • ‘Major conversion’ – e.g. alter ship dimensions, cargo carrying capacity or engine power of the ship, or
  • ‘Mechanical / electrical measures’ – technological measures for improved energy efficiency.

In order to demonstrate the improvements from any voluntary energy efficiency measures, RightShip requires a suitable statement / certificate from Class or appropriate third party detailing the work undertaken and any improvements in energy efficiency.

Please note that ‘operational measures’ (e.g. low friction paint, etc.) cannot usually be isolated from the EVDI equation and are normally not taken into account. It is also important to note that having one aspect of a vessel retrofitted / upgraded will not ensure the same for all other aspects. This is especially so in older vessels that require a re-sea trial, where we are comparing the results to the sea trial recently undertaken with that undertaken when the vessel was new. We therefore cannot guarantee that an upgrade or retrofit would necessarily improve the vessel’s GHG Rating.



Odfjell set about improving the fuel efficiency of their Kvaerner class vessels in close co-operation with MAN Diesel & Turbo, Grenaa Motorfabrik, ABB AS Turbocharging, and Marintek. RightShip were also consulted early in the project to understand the requirements for verification, and also the potential improvements in the GHG Rating.

The upgrades included new energy efficient propeller blades, rudder-bulb and technical upgrades of the main engine, turbo chargers and shaft generator. The combined upgrades reduced fuel consumption and emissions by over 20% – an outstanding outcome.

The Bow Clipper is now amongst the most energy-efficient chemical tankers in the world for its size, and is A rated for GHG emissions. The press release for this case study can be found here.