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The IRS 30% Wood Stove Tax Credit: Which Stoves Qualify?

Q: I understand that the 30% tax credit applies to biomass stoves achieving an efficiency rating of 75% or better. But I see stoves on your website with efficiency ratings high enough to make them eligible for the tax credit, yet their efficiency ratings posted in the manufacturer's brochures are not up to 75%. Can you explain?

Thanks,
Pat Hinds

The short answer: the electron is faster than the printing press.

The long answer: there are two testing protocols used to determine wood stove efficiency: the High Heat Value protocol, and the Low Heat Value protocol. High Heat Value, or "theoretical" testing assumes that 100% of the heat value of the fuel is available for delivery to the room. Low Heat Value, or "real world" testing uses only the percentage of the heat value of the fuel that is actually available for delivery to the room.

Unlike the rest of the world, the US and Canada have traditionally chosen to use the theoretical fuel value of a load of wood (the High Heat Value) as a basis for determining wood stove efficiency. By this so-called North American protocol, a stove that burns a 10,000 btu load of wood and delivers 7,000 btu's of heat into the room is listed at 70% efficiency (7,000 / 10,000).

Test labs everywhere else on the planet take into account the fact that some 10% of those 10,000 btu's must be diverted up the chimney to establish an updraft and prevent creosote condensation, and that those btu's are not available for delivery to the room. Their reasoning is, since those btu's are not available, it isn't logical to penalize the wood stove for not delivering them. Thus, in the above example, a European test lab would adjust the fuel value of that same load of wood to around 9,000 btu's (the Low Heat Value) to more accurately reflect the efficiency of the stove itself. In Low Heat Value testing, our example stove would score 78% efficiency (7,000 / 9,000).

For many years, there has been a growing groundswell within the North American hearth product industry to adopt the European Low Heat Value protocol, as this would level the playing field between US/Canadian wood stoves and their European cousins, and make comparison shopping less confusing for the consumer. When the wood stove tax credit legislation was finalized on June 1st, those prayers were answered: the IRS specified that, for purposes of the tax credit, efficiency values be determined using the "real world" (Low Heat Value) protocol.

At this writing it has already been determined which models exceed the IRS-mandated 75% rating via the Low Heat Value protocol. We've obtained these real world ratings from the manufacturers and published them on our website, and you can bet they'll also appear in the manufacturers' brochures and manuals as of the very next printing. In the meantime, you can download Pacific Energy's qualifying certificate here and Hearthstone's certificates here.

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