A power interface (14) connected to an ultra capacitor (16), a power source (18), and a load (20), with a controller (22) for managing the power interface (14), and monitoring the ultra capacitor (16), power source (18), and demands of the load (20) attached thereto. The power interface (12) selectively switches the circuit between the ultra capacitor (16) and the power source (18), and between the load (20) in response to the level of demand of the load (20) attached thereto such that the ultra capacitor (16) powers peak demand and the power source (18) powers steady demand.