Reducing emissions from shipping has increasingly become a challenge over the last years, both as a counter measure against global climate change and to protect local environments and population from waste, gas emissions and noise.This challenge has been documented both in policy papers, like the Europe 2020 initiative or the Transport White Paper, and in rules and regulations issued by IMO as well as by local authorities. Those legislations as well as emission taxes and an increasing public awareness on green shipping have led to the fact, that low emission ships and shipping has become a key competitive factor both for European shipbuilders (including equipment manufacturers and shipyards) and shipping companies.In response to topic SST.2013.1-2 of the Sustainable Transport Work Programme 2013 the JOULES proposal aims to significantly reduce the gas emissions of European built ships, including CO2, SOx, NOx and particulate matters.JOULES follows an integrated and holistic approach, not only limited to integrating the components of the simulation of the energy grid, but through the consideration of other viable options for emission reduction.The specific optimal solutions for emission reduction and energy efficiency highly depend on the transport or service task of ships, as well as on their operational profile. While a wide overview and holistic assessment of all available energy and emission saving technologies is necessary, industrial breakthrough can only be achieved if the available solutions are selected, adopted, integrated, assessed and finally demonstrated for realistic application cases. The binding element between technologies and applications are modelling and assessment methods and tools. Those are needed to predict the behaviour of complex energy grids, to manage the energy demand in operation and to assess the performance of optimized energy grids both in view of cost efficiency and environmental impact.