In September, the University of Genoa shall present a summer school that covers the theoretical approaches behind the energy efficiency definitions used by IMO and other stakeholders for the marine sector. CO2 emissions and EEDI, EEXI, CII indexes will be introduced. Some energy efficiency devices (i.e. wind assisted propulsion) will be presented and best operational practices will be discussed. The role of the new fuels is introduced. The outcome of the course is twofold: understanding the rule requirements and understanding the principles behind the new available technologies.