I live in SEattle and will have a furnace (95% / variable speed) backup. My propane is getting expensive but electricity is dirt cheap
going back to the original post, it is a heck of a note to purchase dual fuel-propane backup-with an expensive furnace that one would rarely if ever use.
see below climate data for Seattle.
Climate averages for: SEATTLE, WA, 98141
Hot weather Cold weather
Average days per year above 75: 0 Average days per year below 40: 0
Average high temperature: 74.9 Average low temperature: 41.3
It would seem the best choice would be to chuck the furnace for a high eff HP system with var speed air handler and electric backup. just a thought.