Abstract: A hydraulic drive system. In a first embodiment the hydraulic drive system comprises a hydraulic circuit, at least one battery, an electric motor and an alternator. The hydraulic circuit includes a hydraulic pump, a hydraulic motor, and a hydraulic fluid reservoir containing hydraulic fluid. In a second embodiment the hydraulic drive system also includes a combustion engine, a fuel tank, and an electrical generator. In another embodiment, the hydraulic drive system includes primary and secondary hydraulic circuits with the secondary hydraulic circuit featuring throttle functionality. In another embodiment the hydraulic drive system provides power generation to a building such as a family home or dwelling. In a further embodiment the hydraulic drive system is adapted to function as a building power generator system.