|Improved heat transfer led to major|
improvement in efficiency without
any price increase of the EF2.
Enviro appears to have redesigned the stove in an effort to avoid the distinction of having the least efficient stove on the EPA list. In July of 2016, Enviro tested their new version, the EF2-1, only a year after testing the older version, and it came in at 77%, nearly 20% higher than the old version. Now, due to greater scrutiny, they also advertise to consumers that the stove gets 77% efficiency. At the same time they lowered the emissions from 1.8 grams an hour to 1.4 grams an hour. Their carbon monoxide values also went from 25 grams an hour to 7 grams an hour, a dramatic improvement.
At 77% efficient, the new Enviro EF2-1 is one of the most efficient pellet stoves made by a major North American stove company. The average pellet stove is likely to be around 70% efficient, but this may rise as companies like Enviro compete to design higher efficiency stoves. One of Harman’s lower efficiency stoves, the Advance, tested at 67% efficiency. That stove is being discontinued, which could be partially due to its low efficiency. (Harman still claims that the stove is eligible for the federal tax credit for stoves that are 75% efficient or greater.)
The US Stove model 5660 is now one of the least efficient pellet stoves on the market at 62%, but the company still says that it is eligible for the 75% federal tax credit. St Croix makes two pellet stoves, the Hastings and Ashby, that each tested at 66% efficiency by EPA-approved test labs. However, the company website claims that the Hastings is 83% efficient and that its “efficiency ratings are verified by an independent lab.” The Hastings owners manual confirms that the independent lab rated the stove at 66% efficiency. The tax credit is set to expire on Dec. 31, 2016.
The Enviro EF2-1 is also sold by Hudson River Stove Works under the brand names Chatham, Davenport and Kinderhook. Despite the lab test showing the stoves are 77% efficient, Hudson River Stove Works continues to tell consumers that they are 85% efficient. Unlike the manufacturers of automobiles and major appliances, there is nothing stopping wood and pellet stove manufacturers – or their retailers – from blatantly misleading consumers, as Hudson River Stove Works does.
The EPA has made efforts to bring more transparency by requiring manufacturers to post the test lab documents on their websites. These documents show additional details about the stove, including its carbon monoxide levels and emissions results at each burn rate. Enviro is one of the companies that complies with this rule and posts this information so that consumers can see testing information about the EF2-1 here.
In the November update to the EPA list of certified stoves, the EPA added a column for carbon monoxide, as all stoves tested after May 2015 have to test for and report their carbon monoxide emissions levels along with their particulate matter emissions and efficiency. However, the EPA has only input the CO test results for eight stoves as of December 14, 2016. The EF2-1 at 7.4 grams of CO per hour has the lowest. The five non-cat stoves with CO values range from 87 to 186.