Solid oxide fuel cells (SOFC) offer several advantages that are accelerating the research and development of the technology. Recent advances include the improvement of materials and new fabrication techniques, as well as new designs, flow configurations, and applications. The large scale implementation of fuel cells, especially in distributed energy generation, is limited by several factors-one of which is their limited fuel flexibility. Changing fuel typically requires modifying the fuel processing unit to make it possible to effectively convert raw fuel into hydrogen-rich gas. One potential solution allows for the use of alternative fuels without the need for customization of the fuel processor. This solution requires the adaptation of the stack to operate with direct internal reforming (DIR) of the fuel on the surface of the anodes. The present study explores the potential to internally reform methane in the SOFC stack with electrolyte supported cells. The numerical model that was developed for the simulation of the 1300 W stack was validated using experimental data obtained from partial internal reforming. Later, the model was applied to simulate the operation of the stack with complete internal reforming of methane. It was observed that the strong effects of internal reforming on the temperature in the outlets are visible when the current exceeds 22 A. However, it was proven that the DIR-SOFC mode of operation is possible in the considered stack without exceeding the advised temperature limits in the core, and in the outlets of the anodic and cathodic compartments. The model was found to be accurate and the observed relative prediction error was in the range of 1.51-2.38%.