An integrated power supply system includes a grid power source, at least one renewable power source, a rechargeable battery assembly, a DC bus, a bi-directional AC-to-DC converter, at least one first DC-to-DC converter, a bi-directional DC-to-DC converter, and a controller. The bi-directional AC-to-DC converter is coupled to the grid power source and the DC bus. The at least one first DC-to-DC converter is coupled to the at least one renewable power source and the DC bus. The bi-directional DC-to-DC converter is coupled to the rechargeable battery assembly and the DC bus. The controller controls power electricity feeding into and being drawn from the DC bus, thereby keeping a bus voltage of the DC bus substantially fixed at a system voltage.