Molten carbonate fuel cells (MCFC) are a promising alternative power source for distributed or residential power plants. Therefore, thermodynamic models are built in an Aspen customer modeler for the externally reformed (ER) MCFC and internally reformed (IR) MCFC. These models are integrated in Aspen Plus™. In this article the performance of internal and external reforming molten carbonate fuel cell systems are investigated. To this end the gas temperature at the anode inlet is varied to be able to exam the effect of operating temperature on the operating conditions for different modes of MCFC systems in a range between 600 and 700°C. It is found that the operating temperature has more effect on the cell voltage of IR-MCFC system compared to ER-MCFC system. Simulations show that the IR-MCFC system is more efficient than the ER-MCFC system. The cycle efficiency is rather independent of the operating temperature for as well ER-MCFC as IR-MCFC systems.