To get an idea of the reduction in propulsion power and associated emissions by varying the speed and other ship design main parameters, a generic model for parameter studies of tankers and bulk carriers has been developed. With only a few input parameters of which the maximum deadweight capacity is the primary input a proposal for the main dimensions is made. Based on these dimensions and other ship particulars which are determined by the program the necessary installed propulsion power can be calculated. By adjusting the vessel design, i.e. the suggested main dimensions, and varying the speed it is possible to estimate the influence of the different parameters on the power demand. The model is based on previously well-established power prediction methods which have been updated and verified by model test results and full-scale data, meaning that the predictions are up to date according to modern ship design standards. The IHS Fairplay World Fleet Statistics for vessels built in the period 1990 – 2010 is used as a basis for the modeling of the main dimensions. The model can be used to calculate exhaust gas emissions, including emissions of carbon dioxide (CO2), from bulk carriers and tankers. A calculation procedure for estimating the Energy Efficiency Design Index (EEDI) which is presently being developed by the International Maritime Organization (IMO) is also included in the model. Different ship design parameters have been varied to see the influence of these parameters on the EEDI. The paper will focus on the technical and the design measures which can improve the environmental performance and will not take into account operational measures.