Described herein are fuel cell systems and methods of increasing fuel cell system efficiency. The systems include a fuel processor that produces hydrogen from a fuel source and a fuel cell that generates electrical energy using the hydrogen. An electronics device that receives the electrical energy may also include the fuel cell system and a heat-generating component. The invention uses heat from the fuel cell and/or heat from the heat-generating electronics component to preheat a liquid fuel source. This reduces or potentially eliminates the need for fuel source heating in the fuel processor.