What size both furnace (eff) and AC are you replacing? What size living area will be served? I don't understand the sizing of the furnaces that you were quoted. since propane is the furnace fuel, you want to be sized correctly. What is your electric rate? If operating costs are important to you, I would consider pairing furnace with a heat pump.

IMO

Thanks for your reply! We are replacing a Trane XE80 100,000 BTU and a Trane XB1000 model number TTB060D100A0 (couldn't find the Seer). Our electric rate is 0.06413 per kWh plus 0.06211 per kWh generation charges and 0.00570 per kWh transmission charges.

I encourage you to request a load calculation in writing both heating and cooling. I will assume you want propane as part of your heating component. unless there are building type issues, I definitely would want a high eff condensing furnace, 95%+ efficiency since propane is so expensive. I would also pair with a high eff heat pump to take advantage of the operating cost leverage between propane and electric. Just so you are aware, Trane's sister company Am Standard has exact same equipment and usually less expensive. What is your cost/gal for propane?

IMO

Fuel comparison

using 3.00 COP for eff of heat pump at $.13/KWH

95% eff for propane at $2.25/ gallon

Cost per 100,000 btu of useable heat

Electric baseboard: $3.43

Heat pump: $1.27

Propane: $2.59

Thank you! If I prepay my propane, it's actually $1.49 a gallon (at least right now). Would you still recommend the heat pump/high efficiency furnace? Thank you for all of this valuable info.

Using $1.50 for propane, here are the numbers. still a nice savings down to temp balance point where propane furnace would switch over for the colder weather. this gives you flexibility as well. About 25% savings ...

Cost per 100,000 btu of useable heat

Electric baseboard: $3.43

Heat pump: $1.27

Propane: $1.73

you can be assured that propane will not stay at $1.50/gallon...

it's important you get sized correctly both furnace and heat pump. 100 KBTU furnaces are ridiculous...

IMO

Two 100K BTU furnaces seem very over sized for a 4000 sq. foot house seem very over sized. I would think two 60K 95%+ efficiency furnaces would be fine.

"we have propane heat so our bill for heating is about $3000 a year. "

That's a lot of money for heating for the Philadelphia area. You either have a very poorly insulated house and/or your furnaces are operating very inefficiently. You may also have duct work problems. You need to find a contractor who will do a load calculation and inspect your duct work.

Is natural gas available on your street? If it is, then I suggest finding out how much it would cost to bring the service into your house. If natural gas is not an option, then the dual fuel system (heat pump with propane furnace as the backup) is your best option in terms of operating costs.

Thanks! We are in New Hope, PA just outside of Philadelphia. We do have a two story family room so there's a lot of open space.