I am rating efficiency on amount of wood the unit will consume to do the job required. If it will take less wood using storage that IMO is more efficient. I am planning on driving to CT to pick up an Atmos Gs in march.I am just doing my homework before I commit. My brother inlaw is building me a tank out of aluminum, and all its going to cost me is the price of the material. I was thinking 400-500g would be OK? My plan is to run it through fored air via exchanger. I am also thinking two radiators in my grand room. I was hoping I could do this on 8 cords or less of wood per year. I know I can do 8-10 with forced air furnace. Just looking for insight! That I can..I would just be very dissapionted if after everything is hooked up I find out I am burning 15+ cords of wood per year, when I know I could have done it for under 10 going another route. Even though my wood is free I am still basing this on $70 per cord for heat. Five more cord = an extra $350 per year.