High temperature Solid Oxide Fuel Cells (SOFC) systems are high efficient energy conversion systems with low emissions e.g. for residential power applications. The objective of this work is to provide a flexible model of a SOFC system that is capable of predicting system performance in a wide range of operating conditions as well as predicting system lifetime performance based on experimentally determined SOFC performance and endurance curves. The system model is developed using AspenPlusTM unit operation blocks and the SOFC electrochemical model is implemented using the embedded AspenPlusTM Microsoft Excel Workbook. Validation of the model is performed by comparison to experimental results. The adaption of this model to different SOFC system simulation approaches will be discussed. Furthermore for a SOFC based mCHP system development simulation results predicting an electrical efficiency higher than 50 % and an overall system efficiency higher than 85 % for the whole lifetime will be presented.