The design of merchant ships has always had to be centered on economic viability. The main economic drivers amount to the construction costs, crew costs, disposal costs, and fuel cost as it relates to the chosen operational speed. These need to be combined in such a way that the shipowner makes an adequate rate of return on the investment with a given level of risk. The IMO in 2012 highlighted the urgent need to reduce CO2 emissions, as already global shipping accounts for 3 – 4% of anthropomorphic emissions, and this proportion will rise if these emissions are not controlled. Other environmental concerns relate to operational pollution, underwater noise, anti-fouling, ballast water exchange and wave wash. Economic and environmental pressures thus combine to create the need for a fresh appraisal of the estimation of ship propulsive power and the choice of suitable machinery, as well as ship hull design for new-builds. Both issues present the need to minimise propulsive power. Minimising propulsive power can be addressed at the design stage, in terms of hull form design and propulsion design, and during operation which can include the use of suitable changes in trim, route changes and slow steaming. Finally, it helps to reduce emissi