90% of all crago worldwide is transported by ships. These ships use fast amounts of fuels, up to 150.000 litres per day. Because of stricter environmental regulations, fuel efficiency will become more and more important. We4Sea has developed an IT platform, using the unique Digital Twin concept. The technologycombines (measurement) data from ships with meteo data (wave height, wind speed and direction, currents etc) with a full digital simulation model. This gives a current insight into the actual and optimal energy performance of ships, and offers ways to improve it.