There is no lie / part skipped, what that number is meant to tell you is that it reaches its 1:1 point there, so it "works", with diminishing returns, down to t

There is no lie / part skipped, what that number is meant to tell you is that it reaches its 1:1 point there, so it "works", with diminishing returns, down to that point. Which is where it's as "efficient" (to put it that way) as a resistive heater. Obviously you need to take that into account - is the amount of heat you get out of it sufficient for nominal winter temperatures, at its coldest, for where you live? (geographic location and building conditions). As for myself, I have a backup in my wood stove, but I only need it under special circumstances (like last week when it was particularly cold and no electricity for parts of two whole days because I had electricians doing major rewiring in my home).