I am glad to know that the 2800 btu Olympian Wave 3 works.... I might end up getting one,,, and seriously considering a Mr. Heater Big Buddy.
To Brian's point... it depends on several conditions....
heat dissapation through windows
, shell, floor, etc. outside temp, inside temp, insulation, etc.
I just thought it might be ammuzing/educational to read the "science" behind it.