A power unit includes: an energy dispensing/synthesizing system in which a first body of rotation is connected to an output shaft of a prime mover and a second body of rotation is connected to a driven unit via a first power transmission path; a first power transmission system selectively operable between an operating state for enabling power transmission in the first power transmission path and an operating state for disconnecting the power transmission; a second power transmission path connecting between the output shaft of the prime mover and the driven unit; and a second power transmission system selectively operable between an operating state for enabling power transmission in the second power transmission path and an operating state for disconnecting the power transmission, wherein an auxiliary device is connected to a second body of rotation of the energy dispensing/synthesizing system.