Propane-fueled portable power systems with rated power of 125 W and peak power of over 200 W were examined and evaluated. The power generators were able to start up at environmental temperatures from 50 degrees C to -30 degrees C, experience 11 thermal cycles (between 24 degrees C and 740 degrees C) with no noticeable performance degradation and withstand 80 startup and shutdown thermal cycles without failure. After 60 load cycles (16.2 V-12.6 V), the average stack power degradation rate was 0.3% per cycle. Stack longevity of 1000-hour continuous operation was achieved under constant current mode, with an overall degradation of 15% per 1000 hours. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.025205esl] All rights reserved.