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.
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 a 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 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.