Non-cats cleaner than catalytic or pellet stoves in new certifications

In the most recent updated list of EPA certified stoves, 17 more units became 2020 compliant, meeting the 2020 EPA regulations of emitting no more than 2 grams an hour.  While it is not a large sample size, among this batch of newly certified units,  the non-catalytic stoves averaged 1.2 grams an hour, whereas catalytic stove averaged 1.3 and pellet stoves averaged 1.4.  It is not yet clear if the non-catalytic stove designers used new innovative technology or just fine-tuned existing strategies to reduce particulate matter.

Of the 17 newly certified stoves,
non-catalytic models are the cleanest

Many industry experts have argued that the 2020 emission standard of 2 grams an hour favors catalytic and pellet stoves.  But we are seeing some non-cats come in below 1 gram an hour, including 2 of the 5 in this recently certified batch.  Many of the 2020 compliant non-cats do fall in the 1.5 to 2 gram range.  And every once in a while, a stove goes into the lab and doesn't quite meet the 2.0 gram standard, like a IHP stove that recently came out certified at 2.1 grams.  Assuming this unit was not tested with cordwood (which are allowed up to 2.5 grams per hour), this means that the model can only remain on the market in the US for less than 18 months until May 2020, unless the EPA were to approve a sell-through.

Efficiency

The average efficiencies show a less surprising trend: the 13 newly certified non-catalytic and pellet stoves had the same average efficiency – 69%.  The four catalytic stoves, including one hybrid, had an average of 77% efficiency.  These efficiency numbers are typical of averages of all stoves on the market. Pellet stoves have long had the reputation of being a more efficient technology, but over the last several years, as manufacturers were required to disclose efficiencies,  we saw that pellet stoves had a far greater range on the low and high end, with the average being about the same as non-cats.  Even among this small sample, pellet stoves had the lowest efficiency unit (at 60%) made by Sherwood Industries.  Sherwood also made the highest efficiency pellet stove in this newly certified batch – at 77%.

Efficiency could be a more important metric if Congress re-instates the tax credit for residential wood heaters.  That credit was worth $300 but expired in December 2017.  Stoves needed to be 75% efficient to qualify for the tax credit, but manufacturers were allowed to claim eligibility without disclosing their real efficiency, allowing virtually all stoves to qualify.  The practice of exaggerating efficiencies and misleading consumers got to the point that even the industry association, the Hearth Patio & Barbecue Association, changed course in 2018 and recommended that only publicly disclosed efficiencies on the EPA list of stoves be used in the future to determine eligibility.  If the credit is reinstated, there is a chance that the eligibility number could be reduced to 73%, in part to help more non-catalytic stoves qualify.

Carbon monoxide

The other metric that test labs are now required to report is carbon monoxide, another very important test of cleanliness, along with particulate matter.  By far the cleanest technology in terms of CO is the pellet stove. The pellet stoves in this small batch had an average of 0.42. grams an hour of CO, the catalytic had 0.63 grams and non-catalytic stoves had 1.2 grams – almost double the CO of non-cats and triple that of pellet stoves.

A stove's ability to burn off carbon monoxide often tracks its ability to burn off particulate matter.  Of the pellet stoves, the three with the lowest CO also had a lower average PM (1.2 grams an hour), and the three with higher CO had a higher average PM (1.5 grams an hour).  

Overall progress towards 2020

There are 533 stove models on the latest list of EPA certified stoves that are currently in production.  Many of those units will never be changed to become 2020 compliant and many are already not being produced any more.  Industry experts say that the number of stove models will contract as we get closer to 2020, likely in the range of 300 – 400 models.  As of February 2019, 119 models are 2020 compliant.  (The number of 2020 compliant models is consistently under-reported due to delays in processing and notification.)  Many manufacturers may also have completed their R&D and/or their testing but have not submitted the data to the EPA. 

Most stove manufacturers have at least a third to half of their models 2020 certified – including larger brands such as American Energy Systems, Blaze King, Even Temp, Fireplace Products International, Hearthstone, Pacific Energy, Rais, Ravelli, RSF/ICC, Sherwood Industries, Stuv, Travis and Woodstock Soapstone.

However, the two largest value stove manufacturers in the US market – US Stove and Englander – only have pellet stoves certified and still do not have any 2020 compliant wood stoves.   They sell to big box stores, which buy even earlier than specialty retailers.  It is still too early to tell if big box stores will replace Englander and US Stove models with models from other manufacturers, likely at higher prices.  Some in industry hope that the 2020 emission standards will help specialty heath stores regain some of the market share they had lost to the big box stores over the past decade.