Dale, My point was that I might have, at first, picked a different meaning for "backup" than you intended, hence my disambiguation of the overloaded term.
Once upon a time there were units that actually burned natural gas or propane in the outside part of the split system to provide heat for the heatpump to pump when there wasn't much available in the environment. I'm told they were poor and it was not likely that any remain in service around here.
I just recently heard about the high efficiency add-in gas furnace module that is a companion to a heat pump and will go with at least one of those. HVAC guy just got a new software for computer aided engineering of systems and is working some smaller problems that he knows the answers to before tackling my job. I appreciate his caution.
We will have 3 floors in the house andd will have 3 heatpumps. One unit will do the ground and second floor of the shops as two zones with capability to isolate a zone and run an exhaust fan with open windows and not disturb the other floor. The ground floor of the house and the basement will be on a unit in the basement (may remain geothermal even if the other two go to the new high SEER lenox), it does the hydronic in-floor heating on the main floor plus the main floor and basement A/C. The third unit does all of the upstairs, except the second floor shop. May sound some complicated but it isn't. The shops being on their own unit was an IAQ issue. Didn't want to share shop air with house.
I've had real wood burning stoves and fireplace and it was OK but not real convenient. There are units that can be charged with wood and operated by thermostat and will run all day or more or you can use a big hopper on a pellet or corn burning stove for unattended weeks of thermostatic controlled heat with computer controlled setback thermostats B U T it doesn't appeal to me and I want to set things up so that in the future I don't leave a big hassle for my wife. Also, I may just be lazy. I'd rather save my energy for other things, including tractoring.
Not much progress today on house, an inch of rain so far. Am working on suspended porch deck and sunroom design with some help from a structural engineer via phone and email.
Except for the gas furnace to be installed as part of heat pump, the gas heaters are for emergency backup heat WHEN THERE IS NO ELECTRICITY. I don't want to be totally dependent on my backup generator. There is another use for the decorative parlor stoves and the gas log fireplace and that is ambience. They look nice whether operating on not. We have run my mom's gas log fireplace a lot because it looks so nice and heats most of the house that is routinely occupied as opposed to her heat pump which heats the whole house as a single zone.
Remains to be seen what our usage pattern will be in our new house.
Pat