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GHG Emissions Rating



GHG Emissions Rating – what is it?

In 2011 RightShip developed a systematic and transparent means of comparing the relative efficiency of the world’s shipping fleet.

The Greenhouse Gas (GHG) Emissions Rating is an easy-to-use tool containing information on over 76,000 ocean going vessels.

Rather than adopting a ‘one size fits all’ approach, 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, where A represents the more efficient vessel.


Why was the GHG Emissions Rating developed?

Whilst transporting goods by sea represents the most efficient means of moving cargo over long distances, in 2014 the maritime sector emitted nearly 1 billion tonnes of CO2, representing nearly 3% of global emissions.

The GHG Emissions Rating was developed to reduce CO2 emissions from shipping by providing:

  • transparent information on vessel efficiency to inform selection activities,
  • address market barriers relating to energy efficiency in the maritime sector,
  • reward those investing in efficiency measures such as shipowners and their financiers.


What are the benefits of the GHG Emissions Rating?

The key benefits of the GHG Rating include:

  • Benchmark and track emissions per journey and over time – ability to develop a baseline of emissions and an overall carbon-emissions target,
  • Charterers can identify more efficient vessels and in-turn 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, and
  • Ports can reward efficient vessels through port incentive programs – reducing CO2 emissions and other criteria pollutants in port, and for the entire journey.


How are new ships compared to existing ships?

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

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

  1. EEDI – which is a regulatory requirement for new ships developed by the IMO (and applied on an ad-hoc basis to existing vessels), or the
  2. EVDI – developed by RightShip, 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 DNVGL’s methodology review in 2015.


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

The 2007 Denmark paper that initially proposed the EEDI to the IMO at MEPC 57 (MEPC 57/INF.12) stated that "it is not inconceivable that design indices or equivalent may be applied retrospectively to existing ships".

Classification societies regularly undertake voluntary EEDI application to existing ships. Also, as outlined in DNVGL’s review of RightShip’s methodology in 2015 a like-for-like comparison of efficiency is achievable with EEDI and EVDI.


How do RightShip customers use the GHG Emissions Rating information?

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

As of June 2017 eighty-three organisations use the GHG Rating as part of their vessel selection process, including:

  • 52 charterers representing 20% of global trade, factor energy efficiency into their decision-making through RightShip’s GHG Emissions Rating. This accounts for 2.4 billion tonnes of cargo or approximately 31,500 annual vessel movements.
  • 24 shipowners and managers utilise the GHG rating to demonstrate the benefits of investing in efficiency,
  • Various banks, insurers and Ports and Terminals also use the GHG Rating in their business processes.


How can I improve my GHG Emissions Rating?

In order to update the relevant vessel specifications please contact and / or 


My new vessel beats the IMO’s Reference Line – will it be A-rated?

It is a pre-conception that newer is always more efficient. While all new builds are required to comply with the regulatory requirements such as the IMO’s EEDI reference lines, it doesn’t ensure a ship rates well against its peers.

The GHG Emissions Rating compares the relative efficiency of ships against ships of same size and type. Therefore rewarding those ships with superior design and improved technology – whether they are new or existing ships.


How does slow steaming impact the GHG Emissions Rating?

The GHG Emissions Rating is calculated based on a vessel’s design specifications, therefore operational factors such as slow steaming will not improve the GHG Rating.

DNVGL undertook an assessment of the impact of slow steaming in relation to EEDI during their methodology review in 2015.

The comparison of identical vessels (sister ships) found that an efficient vessels performance at design speed will be similar at all set speeds e.g. slow steaming – relative to a vessel of same size and type. Therefore, an A rated vessel will be more efficient relative to a lower rated vessel over an identical voyage. 


Where does RightShip get its information from?

RightShip source data for the GHG Emissions Rating comes from the following hierarchy of data:


Preference / Verification Level

Data Type

Data Source / Example

Table Orange Arrow 

Most preferred /

Highest level of verification

Energy Efficiency Design Index

  • Classification Societies e.g. EEDI Technical Files


Ship specific specifications

  • Ship-sourced data, e.g. sea trial and shop test supplied by the vessel owner / manager


Industry / Third Party data sources

  • Engine manufacturer’s specifications.
  • Data sourced from Ship Yards.

Least preferred /

Benefit from verification

IHS Maritime database

Industry publications

  • IHS Maritime Database
  • Industry publications e.g. IMO publications.


Where does RightShip source specific fuel consumption data?

Specific fuel consumption figures are sourced from respective shop tests, or EEDI technical file, for each vessel. 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 calculation of the energy efficiency measure.


Can I rely on the information RightShip has?

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.

In 2015 DNV GL commenced an independent third party methodology review of the GHG Emissions Rating. The review concluded EEDI and EVDI were comparable on a like-for-like basis, and that the GHG Rating methodology is robust and works as intended. 


What if my vessels’ information is incorrect or missing?

In order to update the relevant vessel specifications please contact and / or 


Why do some sister ships have different ratings?

Generally sister ships will have the same, or similar, GHG Emissions Rating as they are ‘nearly identical’ in terms of build and specifications.

However when the relative efficiency is assessed several factors can influence the GHG Rating including:

  • Verification status – if a vessels specifications have been updated by the shipowner the GHG Rating may be superior to ‘unverified’ sisterships. As DNVGL noted in their 2015 review, there is an incentive for shipowners to verify vessel specifications to ensure the data is up to date and accurate,
  • Changes in specifications – sisterships can be built over a number of years and changes in DWT, engine type, materials used, etc. are not uncommon. Small changes in specifications between sister ships can sometimes impact the relative efficiency and subsequently GHG ratings can be affected,
  • Distribution of peer group – the GHG Rating is a comparison of ships of the same size and type, the peer group. As such, the distribution of the peer ships will impact on the respective GHG Ratings. For example a peer group may be made up of predominantly new ships, as is the case for some LNG tanker peer groups, and therefore ships which are only a few years old may attain an average or poor rating.


Can I use the GHG Rating to estimate emissions for a journey?

The GHG Emissions Rating can be used to estimate emissions from a journey as the GHG Rating is based on an estimated measure of CO2 emitted per tonne nautical mile travelled.

For example if a 300,000 DWT crude oil tanker travelled from Ras Tanura, Saudi Arabia to Long Beach, United States – approximately 11,500 nautical miles – the theoretical CO2 differential between the B rated and F rated vessel is 1,796 tonnes, or 22%.

When translated to bunker savings, a 22% saving across the best and worst performing vessel represent a significant differential for the same amount of cargo being delivered over the same distance. Even taking into account fluctuating fuel prices – e.g. the price of fuel was 75% higher in January 2014 than it was in January 2016 – there is a significant financial advantage to be gained by understanding the relative efficiency of an individual vessel.

When using the GHG Rating as an estimation tool various factors should be considered including the ballast leg measurement (and responsibility for vessel emissions) and operational voyage characteristics such as speed, cargo load, utilisation, and weather conditions.


Are more efficient ships safer ships?

Preliminary analysis conducted by RightShip has established a link showing that ‘greener’ ships (the higher rating vessels e.g. A-C rated) are also safer ships, registering fewer incidents. If this holds true, the benefits to ports of promoting the more efficient ships means fewer breakdowns in shipping channels, fewer incidents and delays, and greater throughput for terminals.

RightShip is continuing to research the links between greener and safer ships, and will update this page when this has been completed.


Whitepaper for the GHG Emissions Rating

RightShip produced a Whitepaper explaining the methodology behind RightShip's Greenhouse Gas Emissions Rating in May 2013.

The Whitepaper has subsequently been superseded by the information contained on this website, and is no longer in distribution. If you have technical questions relating to the GHG Emissions Rating please contact