An electric plenum heater can convert your existing natural gas, propane, or oil furnace into a "dual fuel" heating system. An electric plenum heater gives you the ability to take advantage of the low-cost dual fuel electric rate and the flexibility to use the most cost-effective heating source at any time. The plenum heater is inserted into the plenum of your fossil fuel furnace, which is the ductwork just above the furnace, and uses your existing furnace fan to move air across the plenum heater elements to heat your home. Both your fossil fuel furnace and the electric plenum heater utilize the same thermostat and ductwork. An electric plenum heater can be installed in conjunction with a central air conditioner. When installed with an air source heat pump, it will deliver even greater savings.