This paper develops and applies a two-dimensional computational model that can be applied to evaluate the performance of unit cells on segmented-in-series (SIS) solid-oxide fuel cell (SOFC) modules. The model accommodates detailed heterogeneous chemistry as well as distributed electrochemical charge transfer throughout the entire membrane-electrode assembly. The local charge-transfer rates depend upon local electric-potential differences between the electrode and electrolyte phases. The results predict optimal performance as a function of unit-cell width.