A power plant includes a high temperature fuel cell, a volume expansion heat engine producing mechanical energy, and a combustion chamber coupled to receive from said fuel cell at least a portion of unconsumed fuel and apply high pressure combusted gases to the engine. A reformer can feed fuel to said fuel cell. A distributor distributes fuel cell exhaust fuel selectively to the reformer and the combustion chamber and varies the ratio of exhaust fuel fed to the reformer and combustion chamber in accordance with predetermined power desired from said fuel cell and engine.