With the high cost of energy, whether it be electricity, gas, oil or other sources, finding ways to save money on heating is becoming more and more important. Current technology allows people to burn wood very efficiently to supply heat. Modern wood furnaces, specifically gasifier furnaces, can produce heat much more efficiently than older furnaces, making them competitive with furnaces that run on other sources of fuel.
As Crown Royal Stoves explains, gasification is a process tries to consume all of the fuel by combining high temperatures, wood and very little air in the main firebox. This creates exhaust gases that are forced into a secondary combustion chamber under the wood fire and burned. Temperatures there can reach up to 2,300 degrees Fahrenheit.
Heat exchanger tubes placed in a large water reservoir transfer the heat to the water. The water can now be moved through insulated underground pipes to where the heat is needed, warming rooms using radiators, heated flooring or forced air blowers.
Now that we know how these high efficiency wood furnaces work, we’ll break down how their efficiency is measured, what brands are available and some of the benefits of a high efficiency wood furnace.
How is wood furnace efficiency measured?
Efficiency is measured in different ways for different types of furnaces. Wood furnaces are measured by their overall efficiency. According to the EPA, this is a measure of the percentage of heat provided to a room or space when a load of fuel is burned. The EPA has its own testing method called the CSA B 415-10 they use to determine this percentage.
High efficiency wood furnace brands
Several manufacturers produce high efficiency wood furnaces. Here are some of the most efficient EPA-certified ones available.
- Smart 55 – Topping the EPAs list at 83% overall efficiency, this gasifier furnace is manufactured in Sweden and developed and tested for the US market. With a unique door that cleans the heat exchanger each time it is opened, manual cleanings are reduced from every two weeks to two to four times a year.
- Smart 40 – A smaller size producing only 40kW instead of 55kW, it ranks lower with a 75% efficiency rating.
- Kuuma Vapor-Fire 100 (VF100) – At an EPA-certified 79% overall efficiency, the VF100 is listed as the second-highest in the EPA database and is the only forced air type gasifier furnace we researched. The VF100 also boasts a 99.4% combustion efficiency and is already in compliance with the EPA NSPS Phase 2 standard which exceeds and replaces the Phase 1 standard starting in 2020.
- Classic Edge 350 – The smallest of the three Classic Edge line of high efficiency outdoor wood furnaces, the EPA rated it at 79% overall efficiency. The FireStar Combustion Controller system gives you high-tech control over your furnace even from your smartphone helping you to maximize your furnace’s efficiency.
- E-Classic 1450 – With a 78% overall efficiency, the smaller of the E-Classic models still provides lots of heating capacity. Stepping up to the FireStar XP system gives you even more control.
- GARN WHS-1000 – The smallest of four GARN Wood Heating System (WHS) gasifier furnaces it delivers 77% overall efficiency. A water-cooled combustion air collar maximizes efficiency and keeps the front of the unit cool at all times.
- GARN WHS-2000H – The most common GARN gasifier furnace has a 74% overall efficiency rating with a much larger energy storage capacity than the WHS-1000.
Benefits of a high efficiency wood furnace
A number of gasifier furnace features make them attractive. With advances in highefficiency wood furnaces, their overall efficiency ratings have climbed higher and rival mid-efficiency gas or electric furnaces, while using cord wood reduces their operating costs. Burning wood for heat is environmentally friendly as well, using a renewable resource and producing very low emissions as regulated and tested by the EPA. Surprisingly, heat from high efficiency wood furnaces allows more even temperature control due to the furnace’s water reservoir. And for customers wanting to ‘get off the grid’ and live more simply, gasifier furnaces can reduce dependence on gas or electric power, replacing it with stockpiles of wood to fuel the furnace.
High efficiency wood furnace costs
There are a number of factors to consider when calculating the costs of using a gasifier furnace. These will all vary based on the specific unit you purchase, the region you live in and other individual differences between homes. The estimated ranges here are taken from FurnaceCompare.com’s wood furnace pricing guide.
Wood furnace prices
Prices vary widely, but typically fall between $2,620.99 and $12,494.97, with wood boilers falling in the middle starting at $5,260.00. The Kuuma Vapor-Fire 100 (VF100) is listed at $5,695.00, for example.
Installation costs of a high efficiency indoor wood furnace may average between $3,000 and $5,000, but an outdoor installation may run higher and be as much as $12,000.
Annual operating costs
Annual operating costs vary widely depending on winter temperatures for your area, the furnace you purchase and the area heated. Expect to pay $150 to $400 per cord of wood depending on season and availability. A gasifier furnace can be expected to burn at least one cord of wood per season, but cold regions may require eight cords or even more. Annual maintenance costs should average between $160 and $268.
Compared to natural gas furnaces, a high efficiency wood furnace can save you a lot in heating costs. Assuming that you pay $1,225 to heat your home for 5 months using 250 therms per month of natural gas, and $206 for water heating for 6 months using 210.5 therms per year of natural gas, using a wood furnace could save you $1,431 per year. Over 25 years your total savings could be as much as $35,775.