NOVELTY - The assembly has a fuel source (46) that provides a supply fuel stream at a supply pressure. A supply fuel pressure regulator produces a pressure-regulated fuel stream at a regulated pressure. A fuel cell stack (24) receives pressure-regulated fuel stream and an oxidant stream and produces an electric current at production amperage to satisfy an electrical load. A control system (80) detects supply pressure and selectively controls production amperage based on detected supply pressure by actively controlling an electrical load that is applied to fuel cell stack.    USE - Energy-producing and consuming assembly used in households, vehicles such as motor vehicles and recreational vehicles, boats, microwave relay stations, unmanned transmitters or monitoring equipment. Can also be used in sea craft, residences, commercial offices or buildings, industrial equipment, computers, and signaling and communication equipment.    ADVANTAGE - The control system can be adapted to maintain the fuel utilization in a predetermined range by controlling the electric current produced by the fuel cell stack. The predetermined maximum fuel utilization rate is utilized so as to prevent contamination of or other damage to the energy producing and consuming assemblies and to prevent excessive waste of the supply fuel. The fuel utilization rates are controlled by actively controlling the applied load, so that the improved responsiveness and greater control over the utilization rate are allowed. The applied load actively controlled together with active control of the fuel source based on the flow of unused fuel, so that the greater control of the fuel utilization rate is allowed over a wide range of operating conditions. The active control of the energy-storing/consuming assembly provides quicker response times and greater accuracy in the control over a larger range of operating conditions. Active control of the fuel source can be preferred for prolonged variations in externally applied loads or for prolonged changes in the conditions of the energy producing and consuming assembly.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method of operating energy producing and consuming assembly.    DESCRIPTION OF DRAWING(S) - The drawing shows the circuit block diagram of the energy producing and consuming assembly.    Fuel cell system (22)    Fuel cell stack (24)    Fuel source (46)    Control system (80)    Conductor (88)