Hass said:
don't forget there's burn efficiencies and heat transfer efficiencies... make sure you're looking at the one you're after.
Actually, there's a bit more to it than that. To know the actual heat that is transferred from the stove to the room, one needs to know the
COMBUSTION EFFICIENCY which is high(90% or more) for most new stoves and the
HEAT TRANSFER EFFICIENCY (THERMAL EFFICIENCY) which depends on the thermal mass of the stove, how much heat escapes through the chimney.
Know these two efficiencies, multiplied together and you get the
OVERALL EFFICIENCY.
Sorry, but there's still more.
Wood stoves differ in their ability to store heat and, thus, must be dampered down to prevent all the heat from the fuel escaping into the room in a short time and overheating the stove. This is the
LINEARITY OF OUTPUT of a stove which varies with its mass. Then, at last, there is the
PARTIAL CHARGE EFFICIENCY which is the ability, or not, of a particular stove to handle a small fuel load 'efficiently' without smoldering. This is important in off season days.
So, when a mfg puts out an "efficiency" number, it really does not have much meaning. Buyers would spend their time much better choosing a stove that appeals to them esthetically, is sized properly for their application and has a dealer with some integrity who will guide the person in the right direction, charge a fair price and stand behind the sale if problems develop.
Aye,
Marty