Rheem Classic Series 14 SEER Package Dual Fuel featuring Earth-Friendly R-410A RefrigerantTHE BEST OF BOTH WORLDSThe Package Dual Fuel Unit is a package heat pump with a gas furnace installed in the heat section instead of electric heat that a standard package heat pump features.This hybrid package system allows for both comfort and energy savings by utilizing the electric heat pump for warmth, except in colder periods, which is when the gas furnace would take over to assure maximum comfort and energy savings.