Fuel cells consist of single cells that are connected in series to form a stack. This increases output voltage and therefore decreases current-dependent power losses, but the electric current of the stack has to flow through each single cell. In case of an increase of resistance or a failure of just one single cell the whole stack is affected. The failure tolerance of a parallel connection is higher. The serial and parallel connection of single solid oxide fuel cells (SOFC) is compared under the aspects of failure probability, power drop and stress on the single cells. With both a highly linearized and a complex SOFC model simulations have been accomplished of the connection of two single cells in parallel and in serial configuration. Additionally different connection concepts of 16 single cells were examined. Finally, an outlook on different other source or storage technologies for electric energy like batteries and photovoltaic cells is given.