Abstract: Historiskt sett har låga bränslepriser gjort att fartygsdesign inte inriktats på energieffektivitet för framdrivning. Projektet syftar till att utvärdera betydelsen av variation i driftförhållanden på energieffektiviteten i delsystem och för det totala energisystemet. Trots förändringar under senare år så är fartyg fortfarande inte så effektiva som är tekniskt möjligt, t ex vad gäller låg prestanda såväl i framdrivningssystemet som i de interna energisystemen (pumpar, fläktar, kylning, uppvärmning etc). Projektet avrapporteras bland annat genom en doktorsavhandling.Abstract: Historically, as a consequence of low fuel prices, ship designs have not been focusing on energy efficiency in propulsion. In spite of changes in recent years, ships are still not as efficient as technology would allow. This condition reflects in non-optimal performance not only of the much studied propulsion system, but also on the performance of internal systems (pumps, fans, cooling, heating etc), which are also important parts of the total energy system, as shown in the first part of this project. The overall aim of the second part of the project is that of exploring and evaluating the influence of variable operation parameters on the efficiency of different parts of ship´s total energy system and the resulting influence on the dynamics of the system. This will be achieved by modelling of the systems and evaluation under stochastic input variables and by combining different sub-models into a larger energy system model. One project deliverable is a Ph D thesis.