The combination of a sodium-nickel chloride (ZEBRA) battery and intermediate temperature solid oxide fuel cell (IT-SOFC) to form a hybrid power system intended for automotive applications is examined with the aid of a fuel cell system model. The model allows the operating temperatures of the system to be assessed with a view to thermal integration with the battery. Efficiency curves for stacks and systems are described along with the temperature distribution around the system. Two types of IT-SOFC are compared, one operating in the 500-650 degrees C temperature region and one in the 700-850 degrees C region. The lower temperature IT-SOFC using external steam reforming, and the higher temperature system using partial internal steam reforming, both of methane fuel. (c) 2006 Elsevier B.V. All rights reserved.