Abstract: An arrangement is proposed for a system with at least two molten carbonate or solid oxide fuel cell stacks (1, 2, 3). The cathode flows (14) of these stacks are connected in series while the anode flows (25) are in parallel. All stacks have an internal reforming device for a hydrocarbon fuel. Anode gas is recycled (24) from the stack outlets to the inlets. The invention allows the stacks to be of the same design and this reduces manufacturing costs. The cathode streams between the stacks are cooled by, for example, adding streams of cool air (15) to them. The cathode inlet temperatures can, therefore, be controlled by relatively inexpensive low temperature air valves. The invention allows the system to be designed with few heat exchangers, if any. The per pass utilization of all the oxidant streams and fuel streams are low. The efficiency of the system is typically 4-5 percentage points higher than that of equivalent conventional systems.