This paper explores the determinants of the Energy Efficiency Operational Indicator (EEOI1) by decomposing the indicator into sub-indices that reflect the technical characteristics and logistics of ships. We examine these sub-indices by first constructing a model that mathematically describes the components that comprise the EEOI. A panel dataset of ships’ fuel consumption parameters and transport work is used to estimate these sub-indices. We find that there is a relationship between technical efficiency (EEDI) and EEOI across different ship sizes, but there is a wide dispersion of EEOI values within a ship size class. This can be explained by the variation in logistics factors, with little evidence of correlation between EEOI and any one logistics factor. For all of the types and sizes considered, variations in EEOI can be explained only by considering contributions from a combination of the logistics factors.