Engine-generators generally include a fuel supply, a constant engine speed regulator (governor) and a generator voltage regulator, cooling and exhaust systems, and lubrication system. Units larger than about 1 kW rating often have a battery and electric starter motor; very large units may start with compressed air either to an air driven starter motor or introduced directly to the engine cylinders to initiate engine rotation. Standby power generating units often include an automatic starting system and a transfer switch to disconnect the load from the utility power source when there is a power failure and connect it to the generator.