There is described a fuel cell power system including a fuel processor subsystem, a fuel cell subsystem, and a power conditioning subsystem. The fuel processor subsystem comprises a main module for producing hydrogen rich streams from a hydrocarbon fuel, a balance of plant module for auxiliary components, and a control and electronic module for monitoring and controlling the fuel processor subsystem. The fuel cell subsystem comprises a main module for generation of electric power and thermal energy from hydrogen rich streams produced by the fuel processor module and air, a balance of plant module for auxiliary components, and a control and electronic module for monitoring and controlling the fuel cell subsystem. Each module has individual components attached thereto, the modules being designed and manufactured separately and assembled together to form the respective subsystems.