This paper presents an analysis of the effects of heat sources on performance of a planar anode-supported solid oxide fuel cell (SOFC). Heat sources in SOFCs include ohmic heat losses, heat released by chemical and electrochemical processes and radiation. We take into account the first three types of heat source here while neglecting the last type as it is supposed to be negligibly small. The cell is working under conditions of direct internal reforming of methane and with co-flow configuration. The composite electrodes are dis-cretized allowing the heat source associated with the electrochemical processes to be implemented in a layer of finite thickness. Two cases are investigated, one where the electrochemical heat source is implemented on the anode side (base case) and another where it is implemented on the cathode side. Results for temperature, current density and chemical species distribution of the base case are shown and discussed. Moreover, the effects of magnitude and location of the heat sources are discussed. The results show that including ohmic heating in the cell model does have a significant effect on the predicted cell performance. Comparisons between the two cases indicate that the location of the electrochemical heat source does not affect the cell performance. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.