An apparatus, system, and method are disclosed for maximizing power system holdup time during loss of input power. An energy storage module is included to deliver energy from an output stage of a first power supply to a bus. A power loss module is included to detect loss of power transmitting capability from an input stage of the first power supply to the output stage of the first power supply. A set-point reduction module is included to reduce an output voltage of the first power supply in response to the power loss module detecting loss of power transmitting capability. An isolation module is included to prevent energy flow from the energy storage module to the bus when the output voltage of the first power supply is lower than a voltage on the bus sustained by a second power supply.