Presented here is a novel system that uses an aluminum-based fuel to continuously produce electrical power at the kilowatt scale via a hydrogen fuel cell. This fuel has an energy density of 23.3 kW h/L and can be produced from abundant scrap aluminum via a minimal surface treatment of gallium and indium. These additional metals, which in total comprise 2.5% of the fuel’s mass, permeate the grain boundary network of the aluminum to disrupt its oxide layer, thereby enabling the fuel to react exothermically with water to produce hydrogen gas and aluminum oxyhydroxide (AlOOH), an inert and valuable byproduct. To generate electrical power using this fuel, the aluminum–water reaction is controlled via water input to a reaction vessel in order to produce a constant flow of hydrogen, which is then consumed in a fuel cell to produce electricity. As validation of this power system architecture, we present the design and implementation of two proton-exchange membrane (PEM) fuel cell systems that successfully demonstrate this approach. The first is a 3 kW emergency power supply, and the second is a 10 kW power system integrated into a BMW i3 electric vehicle.