In the past, as much as I could process. I think my record was 14 cords in one year, but I've had other years (last winter) when I think I only burned 6 cords. I'd guess my five year average is 8 - 10 cords per year.
I'm actually running a bit of a new experiment, with these BK's. Instead of trying to push enough wood thru the stoves to heat this joint, wearing myself thin in the process, I'm just loading them on a schedule that suits me. That means 2x loads per day in the stove on the tall chimney (right side in photo above) and 1x load per day in the stove on the short chimney (just left of gazebo in photo above). The 1x load per day is enough for our total heating probably 80% of the time on that end of the house. The 2x load per day is probably enough for our total heating 50% of the time on that end of the house, which is less than ideal, but what my schedule can manage.
We'll have to see how much oil I burn, in this new mode, but it may be less than when I was pushing 10 - 14 cords thru the Jotuls. The BK's put more heat into the house, whereas the Jotuls put more heat into the stone surrounding them, and thus the back yard. This is not a "BK is better than Jotul" thing (although they are), but a "convective works better than radiant" in a stone house, thing.