Hmm! how well will a solar array work during a "Blackout"??
Seriously. Anytime I have experienced a prolonged loss of power, it has been at night and/or stormy weather.
I thing the best source of back up power for any heating system, requiring power, is a generator. Batteries and invertors can only last a very limited period of time with a pellet stove because of the blowers and igniter. True, a very basic stove will operate with out the igniter but you still need at least two blowers (one combustion and the other for heat distribution or you risk burning up your heat exchanger.)
I don't have a home generator but I do have an old (broken down) motor home with a very good generator. Starts everytime and I just run an extension cord directly to the frig and stove.
Steve