Coming from the New York state north country I have a pretty good feel for living in this location. Most north country folks have a main heating system, electric, oil, gas, etc that is backed up by WOOD. What it comes down to is wood being the main source of heat being backed up by the homes heating system.
People also have this in place in the event of a winter time emergency that would shut down electrical service and impact your ability to provide heat. It is of ultimate importance that a back up system is taken into consideration.