On April 8, the EPA posted efficiencies for outdoor wood and pellet boilers, also known as hydronic heaters. Efficiencies ranged from 39% to 78% as measured using higher heating value.
The average qualified outdoor wood boiler is 63% efficient and the average pellet boilers is 70%. However, of the 39 units qualified under the EPA’s voluntary program, efficiencies were only listed for 20 units. Nineteen of the units do not have efficiency numbers available because they were tested using EPA’s previous Method, which resulted in excessively high efficiency numbers.
The highest efficiency boiler in the EPA’s qualified program is Central Boiler’s E-Classic 1450 at 78% HHV. The lowest is Marway Welding’s Phase 2 – 200 at 39%. Another boiler has 47% efficiency, which shows how boilers can qualify for the EPA’s voluntary program emission standards without having high thermal efficiency. Thermal efficiency measures heat transfer from the combustion chamber to the water that heats the home.