Several recent studies have shown that a substantial reduction in emission of greenhouse gases is possible through improvements of operational and energy management practices onboard ships. Operational energy optimization requires processing a vast amount of real-Time and aggregated data. It is argued in this paper that energy management requires a functioning distributed cognitive system, incorporated by humans and technology, which can process the information and adapt its behavior on the basis of that. The offered paper presents the results from the first study investigating energy performance evaluation onboard ships. The research reported in the paper was based on a 1 year multiple-case study of five RoPax vessels operated by one of the biggest ferry companies in the world. The results indicate a number of social and cognitive barriers inhibiting energy management. © 2016: The Royal Institution of Naval Architects.