Well, we always heated with wood (electric backup) and used about 2 cords per winter. It used to be free, but my source dried up so it cost me about $175/cord last 2 years.
I suspect the Harman will burn about 2 tons per season in our very small house, so the price will actually go up a tiny bit (we no longer use electric heaters at all though).
BUT the benefiots are:
1) no more chimney fires and chimney cleanings
2) no more wild temperature swings
3) no more constantly fiddling with the damper and reloading the wood stove 2x per day
4) no more carrying wood with bugs and dirt through the house every day
Soon, I will have hot water coil in the harman, and lower the electric water heating costs.
Also, coal lasts indefinately, so it can be stockpipled. I plan to store about 5 or 6 tons... actually I'd like to go to 6 or 8, 8 tons would be 4 years of heat. Should we have another oil embargo or supply disruption, I'll be ok for 4 years!
All in all, its WELL worth it!