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GHG Emissions Rating

Using the GHG Rating

A vessel’s GHG Emissions 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.

GHG Rating Clear Background

GHG Emissions A – G Rating Scale

Ship Types for Comparison

Ship types for comparison align with the IMO’s documentation and guidance, for example bulk carriers, chemical tankers, containerships, crude & products tankers, cruise passenger, general cargo ships, LNG tankers, LPG tankers, refrigerated cargo ships and ro-ro Cargo ships.

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 similar size and type.

Peer Group Comparison

The GHG Emissions Rating compares the relative efficiency of a ship using EVDI (or EEDI if applicable). The comparison against a ship's peer group – ship of same type and size e.g. +/- 10% deadweight – enables the relative comparison of efficiency.

The peer group comparison is based on the number of standard deviations a vessel’s EVDI (or EEDI if applicable) 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








Size Score

> 2.0

> 1.0

> 0.5

> -0.5

> -1.0

> -2.0

<= -2.0

Area Under Curve









GHG Emissions Rating Key – Normal Peer Distribution

The bell curve below illustrates the percentage distribution with the corresponding letter displayed in the appropriately coloured area under the curve. The x-axis is expressed as a count of standard deviations which matches the Size Score in the key.  

GHG-Emissions -Ratings _2 Clear Background

The example provided below is a 34,627 deadweight tonne bulk carrier with an EVDI of 5.960, giving it a GHG Emissions Rating of C. As can be seen the ship is compared to a peer group of 643 smaller ships (peers – minus) and 567 larger ships (peers – plus), or ships +/- 10% deadweight e.g. within the range 31,164 to 38,090 deadweight tonne. 

Section 2 Existing Vessel Design Index

Vessel Verification – Improving a Vessel’s GHG Emissions Rating 

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

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

  1. RightShip Qi – for RightShip’s subscription customers
  2. – e-mail the environment team who will assist you with GHG Ratings and the vessel verification process
  3. – the public website provides access to the GHG Emissions Rating. A username and password can be setup to gain access.

Verification Information Required

The relevant information required to verify your vessel:

  • EEDI Technical File approved by Class (if applicable)

Or, if the EEDI Technical File is not applicable/available, please provide:

  • Sea trial report
  • Shop tests reports for main and auxiliary engines
  • Capacity factors relevant to the ship type e.g. DWT, GT, TEU, CBM (as applicable)
  • Relevant notations and/or correction factors e.g. CSR, ice class, cubic capacity factors, etc.
  • Innovative technology(s) aimed to reduce CO2 emissions – e.g. waste heat recovery, shaft motors, etc.
  • Additional information as required.

RightShip’s environmental team will review the documentation, update the vessel particulars and provide the updated GHG Emissions Rating.

For further information regarding updating vessel particulars click here.

Retrofitting an existing vessel

RightShip can assist with advice in relation to retrofits and/or upgrades to a vessel. The addition of CO2 emission reduction technology may improve the GHG Emissions Rating.

In advance of planned vessel upgrades you may like to contact to discuss the potential improvements in GHG ratings. 

Retrofit Case Study – Odfjell’s Bow Clipper

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.