Gas leakage often occurs in planar solid oxide fuel cell (SOFC) stacks due to small pressure differentials (2-3 psi) between the process flows and external pressure. This gas leakage can initiate localized burning and degradation mechanisms, which result in lower stack efficiency, reduced stack lifetime, and higher overall cost. A more durable planar SOFC design that can accommodate higher operating pressure would contribute to higher efficiency and more versatile SOFC system integrations. This manuscript examines the performance of a 60-cell, planar SOFC stack up to 45 psia. SOFC stacks can be successfully operated at elevated pressure by containment in a pressure vessel and equalization of the vessel pressure to the process pressure (i.e. anode and cathode gas flows). SOFC stacks display pressure-dependent voltage in accordance with theory, suggesting that an absolute efficiency gain of 2-3% by operating at 45 psia versus ambient pressure (15 psia) is achievable. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.