If a wood boiler has a rating of 60 KW (205,000 BTUs) what does that actually mean? Sounds like a naive question BUT: My confusion stems from the fact that different woods release differing amounts of heat. Add to that the fact that moisture content impacts the release of heat, or at least its useful energy, and you have an almost bewildering range of heat that can be released. Doesn't the amount, kind and wetness of wood in the firebox have a greater impact on the heat that is produced than the machine itself. Using this logic, a 40KW machine packed to the gunnels might easily put out more energy than a 60KW machine loosely packed. Is this logic correct or have I got it all wrong. Take this calculation for example I put in 32 lbs of white ash at 6400 btus per lb and I get nearly 205000 btus of heat. That's not a lot of wood in my firebox and yet that is its rated capacity. I could easily double that weight in wood. Does that mean I would have a 400000 capability? As you see, I am quite confused. Anyone have answers?