Wednesday, February 19, 2014

4 Reasons Why Wood and Pellet Stove Efficiency Numbers are Unreliable

Updated: December, 2016

Confused about stove efficiencies?  You’re not alone.  Even most people in the industry are confused – or don’t want to really let consumers know what is going on.  Granted, it’s complicated and tough to explain stove efficiencies to people who are not experts, but stove manufacturers also have their own incentives for obfuscating what the numbers actually mean. Heating with wood and pellets can be an excellent way to affordably heat your home with a local, renewable fuel.  But the sooner the EPA requires manufacturers to disclose accurate efficiencies, the better it will be for consumers.

Here are 4 main reasons why stove efficiencies are unreliable:.

1. Unlike all other heating and cooling equipment that has third party-verified efficiencies, the EPA did not require that stove manufacturers report their tested efficiencies until May 2015.  Stoves tested after May 15, 2015 have to test for, and disclose, their efficiency, but most of stoves on the market were tested before that so they still do not have to disclose their efficiency. The result is that stove manufacturers routinely advertise efficiencies that are higher than their actual efficiency.

2. This confusion became even worse in 2009 when Congress and the IRS did not  preclude companies from self-certifying their efficiency using the European lower heat value (LHV).  Practically overnight, every manufacturer claimed that all their stoves were at least 75% efficient in order to qualify for the federal tax credit (which at that time was $1,500 then went to $300 and as of Dec. 31, 2016 its expired.)

3. Many pellet stoves have a history of very low efficiency. The EPA used to regulate particulate matter  in pellet stoves in a way that gave them an incentive to have a very high air to fuel.  All the old pellet stoves were grandfathered if they emitted less than 4.5 grams an hour.  Although most pellet stoves on the market today have efficiencies above 60%, there are some as low as 40 – 50%.  Even so, virtually all claim to be at least 75% for purposes of the federal tax credit.

4. Manufacturers have used a variety of different ways to test for efficiency and choose the way that makes their products look most efficient.  Moreover, they can do the testing in their own lab instead of having a reputable, third party lab do independent testing. 

That said, not all manufacturers exaggerate their numbers and most make reliable, good quality stoves.  But there is not a culture of transparency among stove manufacturers, but rather a culture that only discloses what is required by law to be disclosed.  There are 3 things consumers can do to protect themselves from purchasing an inefficient stove.

Buy a stove that reports its actual efficiency results to the EPA.  A handful of manufacturers have recently provided the EPA with third party-verified efficiency numbers, and we hope more will do so in the future.  As of December 2016, there are more than 125 stoves on the EPA’s list with third verified numbers using HHV.  The majority of these are wood stoves.  Few pellet stove manufacturers provide verified efficiency numbers.  Several companies now  provide verified efficiency numbers for all their stoves. For a list of the stoves, click here.  Generally, catalytic stoves are 5 – 10% higher efficiency than non-catalytic stoves and are much easier to keep a fire burning cleanly and efficiently overnight. 

 Keep in mind that with wood stoves, efficiency is not just a function of the stove, but also how the operator uses it.  Make sure to use seasoned wood that is under 20% moisture content to get the highest efficiency out of your stove. For pellet stoves, make sure to clean the stove once or twice a month and have a professional deep cleaning once a year. Otherwise, efficiency can drop significantly as pellet stoves get dirtier.

The Alliance for Green Heat is a non-profit consumer organzation that promotes cleaner and more efficient wood heating. For more information about us and our programs, click here.

No comments:

Post a Comment