Customers have asked us about the savings when adding a Hybrid Heat Dual fuel heat pump to their existing natural gas furnace.  Here is an op-cost spreadsheet showing a 78%, probably 30 year old furnace with metal flue in the Base System column.  This sheet also shows cooling costs and reflects a decrease in air conditioning expenses, too, by using higher efficiency equipment. The Inv1 column shows an upgrade to a Carrier 90% furnace with PVC plastic flue.  Inv2 column shows the return on investment when upgrading to a Carrier 2-stage gas furnace with a 13 SEER heat pump.  Inv3 shows upgrading to a Carrier Infinity 2-stage furnace with a 16 SEER heat pump. We can customize an Op Cost spreadsheet for your home and system that will show an immediate return on your investment that will increase each time utility rates go up.  The Hybrid savings is even greater if you heat with LP gas.     This sheet is based on a 1400 sq foot home built in the 1960s.