We live a bit further south than Bucks County PA, in Anne Arundel county Maryland. My experience with heat pumps here is that most of the time they are"OK", but in the coldest winter weather their internal electric heaters turn on; so you are heating with direct electric heat. How this all works out over the course of a year in terms of cost vs. natural gas, oil, propane seems to be highly variable depending on the exact construction (e.g. insulation, windows etc) of the house and the costs of the various alternatives. If you have to replace your furnace due to floods every 10 years or so, the cost difference of having a heat pump system that survives the flood is probably a good trade off, even if the yearly energy cost for the heat pump is higher. The devil is in the details of each individual situation.