A system provides electrical power and compressed air includes a wheeled hand truck frame, an engine, a compressor, a generator, and a reservoir having several horizontally disposed cylindrical tanks in fluid communication and arranged in one or a few vertical planes. A portion of a lower-most tank of the reservoir is below the plane including the axle for the wheels; and the respective centers of gravity of the engine, the fuel tank, and the reservoir are arranged for relatively greater stability. A control system for the engine, generator, and compressor provides priority response to air demand and/or priority response to electrical power demand by reducing lower priority loads on the engine prior to increasing engine speed. A throttle controller moves the engine throttle from high speed to low speed in response to low demand for compressed air in combination with low demand for electrical power. The throttle controller includes a low demand valve and throttle positioning air cylinder. The low demand valve is operated by an electrical signal asserted in response to detecting a condition of low output current from the system.