High-temperature solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs) are ideal for distributed energy supply operating today with natural gas, which enables development and use of this technology independently from the establishment of a hydrogen infrastructure. Indeed, they offer an interesting transition to the hydrogen economy, offering significant efficiency gains on today's commercially available hydrocarbon fuels while operating effectively on renewable biofuels when these become cost-effective, and ultimately operating with high efficiencies on hydrogen when this becomes widely available. They are also being pursued for use as auxiliary power units for vehicles and in off-grid applications to replace small diesel generators. These types of fuel cells do not require an external reformer to convert hydrogen-rich fuels to hydrogen and this enables the use of a variety of fuels and reduces the cost associated with adding a reformer to the system. They are particularly well suited to CHP applications as they produce high-grade waste heat (or cooling) as well as electrical power. The technology has already been proven by several demonstration projects showing continuous operation over tens of thousand hours