The SOFC has potential as an APU for a variety of future light duty vehicle powertrain systems. In the short term, for the United States SOFC APUs are applicable to heavy duty vehicle and niche light duty applications that need an efficiency electrical source as an 'anti-idling' technology. In the longer term, SOFC APUs are applicable to 3 types of hybrid vehicle. For the conventional/mild hybrid application, the SOFC APU will tend to be very small (1 to 3 kW), and matched to required thermal, syngas and engine off electrical functions. This fits with luxury vehicles or heavy use conventional vehicles (taxis, shuttle buses, ambulances, police vehicles, contractor vans etc.) For the full hybrid application, the SOFC APU is also likely to be very small (1 to 3 kW), and linked to HVAC functions (because substantial electric capability is already available from the battery). The APU can extend the engine-off electric capability and can be an important enabler to making HEVs more efficient and more attractive in cold weather and, at the same time, increase the range and utility of the vehicle. While a 10 kW SOFC APU is not near to production at the cost and performance level for this application, its potential as a highly efficient APU technology with excellent potential for thermal integration into HVAC functions and for integration with distributed energy and micro-cogeneration applications and new synergies between transportation and stationary power systems. SOFC APU and Lithium Ion battery systems are important enablers for several future powertrains. The SOFC Li-Ion range extender EV is the most adventurous scenario (and probably the least market driven in the short term). However it has exciting potential as an ultimate 'low CO2' scenario for low intensity, mass market urban transportation. While SOFC looks to have superior attributes in efficiency, emissions, by-product heat and packaging, the range extender architecture could be deployed with conventional (diesel or gasoline ICE), incremental (Stirling or microturbine) or even PEM APU technology. So the Li-Ion battery is the must have technology in the short term, based on weight, volume and packaging advantages over other battery types.