Tom I have been following your other thread and I believe I said that for your area/climate, I recommended a matching var speed air handler paired with a HP rather than backup gas furnace. There may be two obstacles to this type configuration. 1.size of air handler and its location 2.whether your electrical service/breaker panel requires an update to handle the backup electric strips. and yes, you do require electric backup strips both for defrost function, aux heat when needed, and emergency heat if you have breakdown situation on outside HP condenser. If the electric service update is necessary but is cost prohibitive, then go with gas furnace backup-only 80% eff var speed would be more than adequate. now to get on my soapbox for a minute. Trane is clearly falling behind on dual fuel applications.I would not want to leave $1500 on the table due to their shortcomings. I am not a Trane basher as I have a 4 yr old Trane dual fuel system and have generally been very pleased especially with my savings over gas. To date, I believe I have used about 60 therms of nat gas backup this winter as opposed to relying almost exclusively on my Trane HP. My Trane furnace is an XV90 that has been phased out for the XV95-93% eff vs 95% eff. I have never used the second stage on the furnace and really the furnace is overkill for my home along with my SE area/climate. on a three ton Trane XL15i HP, there were 6 configurations that qualified for the tax credit-all with air handlers,none dual fuel. on the Lennox three ton XP14 HP, there were about 18 configurations that qualified-both air handlers and gas furnace.(No XP15 HPs qualified at all) and for Carrier's three ton Performance 15 "H" mdl, there were over 100 configurations that qualified-both air handler and gas furnace backup. If you require the gas furnace backup, then you must look at the Carrier systems. the gas fireplace backup is nice but it should not be depended on as the exclusive backup/emergency heat for your home. let me know if you have questions. IMO

I wouldn't recommend the TUX1D furnace over the TUH2D (variable speed), especially for more money. Ask dealer 2 why he's quoting a 5 ton versus the 4 ton in estimate 1. A load calculation needs to be done. Overall dealer 2 is quoting larger equipment. I thought the furnace had a 10 year warranty if registered online with Trane within 60 days - something to ask about. The prices do not sound all that unreasonable since it includes all ductwork and a dual fuel, high end heat pump system. You should be getting a better thermostat, such as the Honeywell IAQ or TCONT802. I would expect around a $10k price tag since it's a complete installation with new ductwork. Looks like your area's prices, or these dealers' prices, are running higher. I'd get another estimate.

Tiger said, "this post deserves further and more complete explanation..." Amen. First of all, where are you located? If you have any degree of heat/humidity in the summer, you need to size the HP for COOLING. To be offered a choice of HP with a 2 ton spread is preposterous, not to mention how your duct system will function. Info please. Heat calc, anyone? V

Ok, you've confused efficiency with actual cost. Very easy to do. Gas will always be the least efficient, because some of the heat is exhausted out thru the flue of the home. When natural gas is burned properly, the exhaust is carbon dioxide and more efficient furnaces will also produce some condensation along with that carbon dioxide. (CO2) When there is improper combustion the furnace can produce carbon monoxide. (CO) In most instances of this there is a lack of combustion air, improper installation etc. A heat pump will never produce any exhaust 'at the home' of which it is installed. Heat Pump efficiency: there is no exhaust 'at your home' to run the heat pump. Depending on how the electricity is produced in your state. Some power plants use natural gas for power production... so in reality there is 'efficiency' losses thru waste or exhaust fumes. Dual fuel options: Prices change over time and thru various times gas costs can run higher. But with large recent discoveries natural gas will likely be the cheaper option, especially for areas that have average daily temperatures below 32 degrees. A heat pump loses efficiency due to running defrost mode when temperatures are less than 32 degrees out side. If your electric rate is high in your area then you would likely pay more to run a heat pump than you would a natural gas furnace. Heat pumps mainly exist for those who do not have gas available in their area, as compared to electric strip heat the cost effectiveness can pay for the heat pump within a few seasons. Typically in a electric strip set up for an average home you could have 4 heat strips that run 20 amps per strip. Under full load that is 80 amps. In comparison a modern day heat pump running in heat mode may use 10-15 amps under full load. Those operational savings in comparison to electric strip heat add up quick.