Abstract: A heating system includes an electric heater having coupled thereto a temperature controller and a power activation relay switch coupled to the temperature controller and a meter system coupled to a power terminal on the electric heater to provide an interruptible supplemental heating system for use in residential or commercial buildings. The heating system provides electrically generated heat to supplement a primary heating system which generates heat using fuel oil, fuel gas such as natural gas, propane gas, or other fossil fuels. The electric heater can be an electric resistance heater coupled in series with a primary furnace powered by fossil fuel. When the electric resistance heater is activated, the heat contributed by the heater reduces the required heat output of the primary furnace by a corresponding amount of thermal energy. In one embodiment, an electric utility provides electric power to the electric resistance heater at a reduced cost on an as available, fully interruptible basis.