The GHG 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 vessel’s 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.