A methodology with a practical orientation is derived from experienced issues in the application of modelling and simulation. This methodology allows the simulation based comparative studies in terms of their replicability, comparability and modelling close to reality. It is used to investigate development options of utility sized power plants with regard to efficiency improvements and/or CO2 emission reductions. The study compares current state of the art hard coal fired and lignite fired steam power plants and their improvements by increasing steam parameters, lignite pre-dying as well as the application of CO2 capture by post combustion or oxyfuel technology. Furthermore, the impact of using different gas turbine models for natural gas fired combined cycle power plants are studied.