I'm really glad to have found this site and look forward to hearing your views.
After abusive local electric rate increases, I'm going dual fuel to cut next Winter's heating bill. I got 5 quotes on adding LPG to my 10 year old Rheem 13 Seer A/C/Heat pump. Of Trane, Lennox and 3 Rheem quotes, all the Rheem guys came in lowest. The winning quote replaces the thermostat with a Honeywell (no model noted) dual fuel thermostat. I did upgrade from the Classic 90 to the Prestige 90 updraft modulating furnace, plus opted for the Honeywell HE265 Humidifier. I live in Central Maryland (got down to 6 degrees many nights in Jan/Feb this Winter).
I know that the 10 y.o. A/C+Heat Pump will probably go up in a few years, but I'll fix it at that time. I'm too busy recovering from $600 monthly electric bills to replace everything at once.
After signing on the dotted line, I realized one reason the winning bidder (a listed Rheem dealer) came in lowest- he is not replacing the "coil" like the other guys. If this is not 100% optimal, I can live with that, but I wonder if it matters that much. One guy said replacing it would turn my 13 SEER into a 14 SEER. I'm thinking I'll need the HP/A/C replaced in a few few years and I'll do it then, but perusing the Rheem parts web sites, I see they have a coil optimized for dual fuel setups. Is this coil replacement considered optional or necessary?
One other caution I have is that my new contractor said Rheem doesn't make a dual fuel thermostat. After googling (for 5 seconds) I found the RHC-TST401MDMS.
I'm going to find out what thermostat he's using before the install next week, but I'm wondering how much that matters, too, since it is "dual fuel".