I have only been in this house since July 2004. I had duel fuel at my last place also so I was familiar with it.
Both of these systems had "issues".
They could have qualified for the wall of shame. The previous owner/builder of the house had spent a lot of money on what was 2 top of the line systems at the time which was HP's and condensing furnace's for aux heat.
They were never installed right and had never worked right since new. Of course the home owner had no idea they were getting almost no benefit from the extra money they spent. The home stayed warm, thats all they knew.
Thats how my quest began and I decided to replace rather than invest any more in the old ones.
I had the old systems last winter and even though I did rig the controls to use the HP's as much as possible I used way too much propane.
I spent many hrs researching and ended up with the Carrier Infinity systems and elec aux heat.
I am very hard to please but I am very pleased with these systems.