In this work a detailed analysis of the overpotentials inherent during the operation of a solid oxide fuel cell (SOFC) is presented. The study is performed in order to evaluate the effect of the design of the current collectors on SOFCs performance. The analysis is carried out by means of numerical simulations in different current collector configurations consisting of straight channels in which their width is varied. Special attention is paid in the ohmic and concentration losses which are directly related with the design of the current collectors. Polarization and power density curves are obtained for different current collector designs operating at the same conditions. The ohmic losses were directly affected by the ratio between the gas channels-electrode interface area and the active area. Increasing or decreasing the area ratio around a certain value causes the ohmic losses to increase exponentially. Moreover, the concentration losses showed an opposite behavior when compared with the ohmic losses. The best performance was obtained when the ratio between the gas channels-electrode interface area and the active area is about 0.36. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.