Presented herein is a fuel cell assembly, including a reformer housing, a reformer region within the reformer housing for producing hydrogen, a vacuum housing for containing the reformer housing, a low-pressure insulating region between the reformer housing and the vacuum housing for providing thermal insulation, radiation shields disposed about the reformer region for providing radiation insulation, and at least one proton-exchange-membrane fuel cell in fluid communication with the reformer region. The vacuum housing may define a volume of less than about 30 cubic centimeters. The fuel cell assembly may produce less than about 100 watts of power. Also disclosed are related methods for reforming fuel.