Efficiency Ratings

brakatak Posted By brakatak, Jul 29, 2013 at 4:33 PM

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  1. brakatak


    Jul 1, 2013
    SE Mass.
    How important are these? and what do they mean exactly? Comparing 2 inserts, I see one rated at 84.7% (enviro boston), and the other at 76.9% (lopi freedom).

    Does this just mean that using a higher efficient insert will take less wood to get the same amount of heat?
  2. begreen

    Staff Member

    Nov 18, 2005
    South Puget Sound, WA
    Not super important. There are different ways of measuring efficiency. One being how cleanly it burns and the other how much of the fire's heat is delivered to the room vs up the chimney.
  3. Backwoods Savage

    Backwoods Savage
    Minister of Fire

    Feb 14, 2007
    I agree and most tend to overstate it. I recall going to stove shops that claimed from 90 to as high as 98% efficient. Naturally I wrote off that stove shop right away. ;lol Most will also tend to over-rate how large of a home the stove will heat. They also won't tell you that you should already have your wood well before you buy the stove! This is extremely important.
  4. Sprinter

    Minister of Fire

    Jul 1, 2012
    SW Washington
    A bit simplistic, but that's the idea.
    I'll follow up on this a little. The efficiency rating you normally see in ads is normally a blend (the product, actually), of the combustion efficiency (how clean the burn) and transfer efficiency (heat transferred to the room), based on a standard test protocol in an EPA accredited facility. Of course, these tests are done with the stove operating under optimal conditions, conditions that most owners rarely meet in real life, since there are a myriad of factors at work.

    All EPA stoves can be considered high efficiency with little practical difference between models. However, catalytic stoves are generally considered to be more efficient than non-cat stoves when operated properly, although even there, the differences can blur.

    Edit: Just to be more precise, combustion efficiency is how much of the available energy in the wood is released by combustion. How clean the burn is, would be the grams/hr rating.
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