Abstract: A method and apparatus for controlling the normal operation of a hydronic heating system, (including AC powered, gas-burning hot water boiler, multi-zone systems) using a DC power source, such as battery power, as the primary continuous source of electricity. Control functions minimize the consumption of electric power during normal operation, and eliminate standby electric consumption in order to extend the life of the batteries and maximize the run-time of the heating system. A DC to DC converter supplies low voltage DC power to the zone thermostats, and also supplies the proper voltage through zone relays to operate DC zone pumps. By allowing the use of DC power for the thermostats and zone pumps, the system eliminates the need for transformers, zone valves, and AC circulators, resulting in a large savings in electrical consumption and the elimination of the standby electric demand (“phantom load”) common in conventional hydronic heating systems.