A DC power system receives AC electrical power and DC electrical power from separate first and second sources simultaneously. The DC power system delivers DC electrical power to an output for use by a load requiring DC power. The DC power system includes a converter to convert AC electrical power to DC electrical power and a power sharing control device to control and distribute the DC electrical power to an output. The first source of DC electrical power includes a storage battery, which provides standby DC electrical power to the DC power system. It also includes a power sharing device, which maintains the storage battery fully charged for use at peak loads, when the DC output electrical power is insufficient to meet the DC load. The second source of DC electrical power is a cogenerator such as a fuel cell, a thermo photovoltaic generator or an internal combustion engine and an alternator for generating and delivering DC electrical power to the power sharing device, while producing and delivering waste heat for use of an external load requiring this heat.