The unproductive time that ships spend in ports represents a substantial waste of resources for the shipping company. The calculated increase in energy efficiency of 2–8 per cent falls in the same range as that provided by Faber et al. (2011), but is lower than the assessments by Bazari and Longva (2011). Some areas of further interest have been revealed in this study, and in previous related work, that are key issues in understanding the potential for increased energy efficiency in shipping through increased port efficiency.