In this paper, we investigate the performance of a newly proposed power and heating system using proton-conducting solid oxide fuel-cell (SOFC-H+) for vehicular applications and its optimization for the best possible performance in terms of power output and efficiency. We also study heat recovery option here to improve the performance. Taking this into account, we calculate the exergy efficiency as 60-75% as a function of the air stoichiometry. Also, we show that by allocating optimal volumes to the main components it is possible to maximize the system's volumetric power output. The optimal allocation is quantified by the ratio of stack's volume versus the overall system volume. Both system configuration and performance depend on the optimization objective that may aim to obtain either maximum power density (or useful space on-board) or maximum efficiency (or driving range). if the optimization is performed for a maximum efficiency. the stack occupies about 75% of the total system volume, but the compactness is reduced by about 40% with respect to the maximum power density design. (C) 2008 Elsevier B.V. All rights reserved.