.... is the efficiency of the space you are trying to heat.
I see folks post about the square footage they are heating, the amount of cords they consume per week, and how the claims of the boiler manufacturers are out to lunch..... and I say: Who cares?
I mean, if the space you are heating is as efficient as if it had a 20' hole in the roof, does it really matter?
When I hear guys saying they will burn 12-18 cords of hard wood this winter (and seem happy about it), it blows me away. i couldn't fathom even thinking about burning that amount of wood. Last year in my air tight, I heated my entire 2691sf high efficiency home with just over 4 cords. That was burning softwood in western Canada, burning 24/7 and running my LifeBreath system at least 12 hours a day in -30 weather.
Yesterday I spent the day with a couple helpers insulating my new building. I personally inspected and remediated every area that had the possibility for heat loss. I spent more time and money where it counts..... in the design, construction techniques, building material .....to gain the most efficient building in respect to how much time and effort it will take to heat it.
If the building that is being heated is efficent, maybe the OWB manufacturers claims are more closer to the truth?
I will soon see.