I'm starting to rebuild our forced hot air system after getting the house on a new foundation. All ductwork is now well insulated. However, before having a new plenum made up, I am pondering either replacing the propane furnace or just keeping it for backup and switching to a heat pump for primary. We have no need for air conditioning, so I am less interested in the SEER efficiency than HSPF. The newest air heat pumps are getting to the point where they make geothermal less attractive. Can I get some feedback on what systems people are using? What company and model? What climate are you in and how well do you like it for heating? At what temp does the backup heat kick in? What is its age and what was the cost of installation? BTW, it looks like Nyle products is about to come out with a heat-pump boiler designed to work in cold climates. I've requested more info on this system.