A fuel cell system including: a reformer to convert a fuel into hydrogen; a reformer chamber to contain air heated by the reformer; a fuel cell stack to convert the hydrogen into electricity; a first pump to supply an oxidant to the stack; and a second pump to supply the heated air to the stack, to preheat the stack. The system may also include a controller to control the operation of the system, such that the heated air is not supplied until it reaches a predetermined temperature, and the oxidant is not supplied and the stack is not operated, until the stack reaches a predetermined temperature.