Outdoor wood furnaces offer the potential for dramatically reduced heating costs while keeping your home very comfortable. Outdoor wood boiler costs start at about $6,000 for a small unit with installation and rise to more than $12,000 for a large system that also supplies usable hot water for your home, garage or pole building, an outdoor spa or pool.
In short, outdoor wood boiler cost is $6,000 to $12,000 or more based on the size and features of the model you choose.
This buying guide is about outdoor wood boilers, the most popular type of outdoor heating system. These systems heat water, and the water carries the heat indoors where it is transferred to a boiler/hydronic system or a forced air system. More details on how they work are below.
Outdoor boilers are also called OWBs, outdoor water furnaces and outdoor furnaces. The last term is confusing, because it is also used for outdoor stoves that create hot air only, not hot water.
What This Outdoor Wood Boiler Guide Includes
Here’s are the contents you’ll find below. Read through all sections, or jump to a topic of interest.
- How an Outdoor Wood Boiler Works
- Standard and Gasification Boilers
- Dual Fuel Systems with Gas Heat
- 3 Types of Alternatives to Wood
- Wood Boiler Options and Features
- Outdoor Wood Boiler Prices
- Pros and Cons of Wood Boilers
- Cost of Heating with Wood
- Top 3 Outdoor Wood Boiler Brands
- Tips for Buying an Outdoor Wood Boiler
How an Outdoor Wood Boiler Works
If you’re familiar with boiler heating, the basics are the same.
Fire: The boiler has a firebox, also called a heat exchanger, where the fuel burns.
Water: The box is surrounded by a “water jacket,” which is water circulated around the heat exchanger to be heated to about 180F. The water is circulated by a pump through insulated pipes buried in trenches between the boiler and your home, outbuilding, garage or whatever else you’re heating.
The Exchange of heat: Parts are installed in or adjoining your indoor equipment that allow the transfer of heat from the outdoor boiler’s water to your indoor heating system.
Water to Water Systems
This means heat is transferred from outdoor water to an indoor boiler system. Water to water. This is accomplished with the installation of a plate exchanger in most systems. It is where heat in water from the outdoor boiler is transferred to water from the indoor boiler. The heated indoor water is then circulated as usual to radiators or through in-floor hydronic tubing. While some manufacturers state that their outdoor water furnaces can be connected directly to indoor lines, most installers insist on using a plate exchanger due to the differences in water pressure in each system.
Water to Air
If you have a forced air system, a heat exchanger is installed in the plenum connecting the furnace or air handler to the ducts. Hot water from the outdoor wood boiler circulates through the heat exchanger, and the blower in the furnace or air handler passes air over it to heat the air and distribute through the ducts.
In either system, outdoor water leaves the indoor heat exchanger and travels back to the outdoor furnace for reheating.
Standard and Gasification Boilers
You might be familiar with the concept of standard-efficiency furnaces or boilers and condensing models. The condensing units get more heat from combustion gases that are lost in the exhaust of standard units. The difference between standard and gasification boilers is much the same.
Standard wood boilers burn just the wood. You might be thinking, “what else is there to burn?” Well, gasification boilers burn the wood and burn the gases created because those gases are loaded with combustible fuel that would otherwise be lost. Think of a campfire. The smoke rising from the fire is rich in fuel that could be burned with enough heat and a boost of oxygen.
Gasification Boilers – How They Work: Oxygen within the firebox is depleted by initial combustion of the wood. That process is called primary combustion. In gasification, oxygen from outside the furnace is pumped into the combustion chamber. There’s already enough heat present, so the added oxygen causes the unburnt gas and smoke to ignite. The result is getting 30% to 50% more heat from the same amount of wood. This video from Central Boiler is helpful and fun too (and we have no connection with Central Boiler).
Because the wood, gases and smoke are burned more completely, there will be less smoke and smell coming from the outdoor unit – and both you and your neighbors will appreciate that. Combustion that is more complete also means less ash, soot and creosote to clean.
Dual Fuel Systems with Gas Heat
Wood is an outstanding fuel, but for one drawback – wood needs to be added every 10 to 48 hours depending on the capacity of the wood boiler and how much heat is being demanded. When the wood is burned, the fire goes out, and there’s no more heat. That’s inconvenient if you plan to leave home for a day or a week during cold weather and don’t want your home freezing.
Dual fuel wood boilers are the answer. The units can be outfitted with auxiliary propane, natural gas or fuel oil burners for times that heating with wood isn’t convenient or possible. Sensors in the outdoor wood boiler signal the gas burner to fire up when the temperature in the OWB drops below the thermostat setpoint.
Dual fuel setting options: Systems that heat with multiple fuel sources typically have settings for how you wish to use the dual fuel feature. 1). Start a heating cycle with gas or oil for rapidly heating water in a cold boiler while the wood fire gets going. This immediately creates enough heat for gasification burning. 2) Switch to the backup fuel when the wood fire dies down. 3). Heat only with the alternate fuel.
3 Types of Alternatives to Wood
We’re focusing on wood (firewood/fuelwood) in this guide, since it is the most popular fuel source. For many, it is also the cheapest.
But we know PickHVAC readers are informed consumers, so you should know about other types of outdoor water furnaces besides wood heaters.
Wood pellet furnaces: Pellets are made from sawdust and binder, and the furnaces that burn them cannot use firewood. Their advantage is that they have low moisture content, so burn efficiently. By comparison, seasoned wood averages about 20% moisture content, and since water doesn’t burn, your losing efficiency with wood. Efficient burning means less smoky smell too, so they’re a good choice when heating with an outdoor boiler in a neighborhood setting. The furnaces contain a firepot where combustion occurs. It is smaller than the firebox on OWBs, so the firepot is fed continuously by a hopper attached to the outside of the furnace.
Corn: Dried corn also has a low moisture content, so burn cleanly with little smoke. However, the sugar in the corn forms a type of ash commonly called “clinkers” that must be cleaned from the firebox daily or slightly less often. Corn is difficult to ignite on its own. The best technique is to get a fire started with pellets and then add corn from a hopper once the material in the fire pot is red hot.
Stoves that burn pellets can also burn corn, and vice versa, but they must be slightly modified to do so. The two fuels have similar burning efficiency. If you live in corn country, corn will be the cheaper fuel source. In the Northwest and other heavily wooded regions, pellets might be cheaper. Both pellets and corn must be fresh – material from the previous heating season absorbs too much moisture during summer to burn efficiently and cleanly. Corn and pellet furnaces are referred to as biomass furnaces.
Coal: Popular where coal is abundant, coal-burning outdoor furnaces produce an enormous amount of heat. They best serve very large homes or properties where more than one building is being heated. Some wood-burning furnaces such as the Heat Master MF eSeries can also burn coal.
Wood Boiler Options and Features
Cost varies quite a bit with the available options and features.
Size: Firebox capacity ranges from about 10 cubic feet to 24 cubic feet or more. The larger the capacity, the more BTUs the furnace can produce. Common ranges for product lines from the top manufacturers are about 150,000 BTU to 240,000 BTU for residential use, but units with capacities above 400,000 BTUs are available.
There’s another factor – an important one – regarding size. The amount of heat a unit creates can be controlled with dampers that limit oxygen and cause the wood to smolder for less heat or add oxygen and produce a roaring flame for more heat. The advantage of larger fireboxes is that the fire can burn longer. A 24-cubic foot furnace will burn for 2.4 times longer than a 10 cubic-foot unit when both are churning out the same BTU levels.
Water Capacity: This is related to size. The capacity range for residential wood boilers is about 100 to 325 gallons of water. Water capacity affects how large a home the boiler can serve and how many BTU it can produce.
Domestic Hot Water: With additional piping and a plate exchanger, the OWB can supply enough hot water to heat the water in your water heater. The water from the boiler isn’t mixed with the water in your water heater. Instead, hot water from the boiler flows in and out of the plate exchanger. Water from the water heat flows through it too. Heat from the boiler water transfers to the water heater water.
Using this technology, your outdoor water boiler can be used to make hot water for domestic hot water use or for a heated pool, hot tub, sauna and other purposes.
Outdoor Wood Boiler Prices
Now that you have an idea of the equipment options available to you, it’s time to explore costs. Very handy homeowners sometimes install their own boilers, so we break down costs into three areas.
- Wood boiler cost is for the boiler only.
- Installation supplies include piping and parts required for water to water and water to air applications.
- Labor cost is just the cost to install the unit and installation materials required. This is what you’ll save – or should we say earn, because it’s hard work – by installing the unit yourself.
|Wood Boiler BTUs||Boiler Cost||Supplies Cost||Labor Cost||Total|
|Up to 100,000||$3,300 - $4,400||$300-$550||$2,400 - $4,000||$6,000 - $8,950|
|100,000 - 150,000||$4,250 - $5,400||$365 - $625||$2,550 - $4,300||$7,165 - $10,325|
|150,000 - 200,000||$5,325 - $6,200||$400 - $650||$2,550 - $4,300||$8,285 - $11,150|
|200,000 - 300,000||$5,885 - $7,775||$425 - $700||$2,700 - $4,500||$9,020 - $12,975|
Note on DIY Installation: This is moderately hard to difficult DIY project. Our recommendation is that you consider it only if you have good plumbing skills and experience.
Once installed, the unit has the potential for leaking, and water can do lots of damage in a short amount of time. Additionally, that water will enter your home at about 175F, so with leaks comes the very real possibility of scalding. Most manufacturers offer tutorial videos on their sites for DIY installation. Watch them all, and then test the system “cold” before firing up your wood boiler.
Pros and Cons of Wood Boilers
There’s plenty to like about outdoor furnace boilers and a few concerns too.
Here’s what makes outdoor wood furnaces so popular in areas where fuel is abundant.
- Low or no heating cost: Many wood boiler owners live where they can gather their own firewood. It might require investing in a chainsaw and safety gear, and it helps to have a pickup truck or trailer for hauling the wood. Firewood can be gathered on public lands from downed trees and standing snags. A permit is required. This link from the USDA Forest Service gives rules for gathering fuelwood in federal lands such as National Forests. If you have to buy firewood, your fuel costs will still be the lowest of any common home heating fuel. See the comparison below.
- Low or no hot water costs: Most homeowners choose a boiler size that can also provide their domestic hot water (DHW) needs. Savings can add up to more than $1,000 per year in large households.
- A warmer home: Many homeowners keep their thermostat below 70F, skimping on heat to cut down on the high cost of heating with electricity, gas or oil. When you dramatically cut fuel costs with wood, you won’t mind turning up the heat to a comfortable level.
- Heating multiple locations: Large outdoor wood furnaces can be used to heat your home and the garage, pole building, greenhouse, hot tub or other place you want affordable heat.
- Versatility: Outdoor wood boilers work with most indoor systems including boiler and forced air systems. This minimizes cost when adding the small amount of equipment like a heat exchanger needed to connect the two.
- Less smoke than before: Being downwind of a wood boiler can be unpleasant, for all the smoke one can make. New gasification boilers significantly reduce emissions. They burn cleaner with little or no smoke and smell.
- Less mess and smell than indoor stoves: It’s hard to prevent your home and its inhabitants from smelling like smoke when combustion is indoors. With an OWB, all the mess is outside.
- Reduced risk from wildfires: You didn’t expect this benefit, perhaps! It’s now understood that clearing forests of dead timber removes fuel that would accelerate forest fires and make them more damaging and deadlier.
Here’s the other side to owning an OWB.
- High initial cost: Outdoor furnaces installed cost more than indoor gas or oil furnaces, heat pumps and boilers. Financing is available from many sellers, but financing means finance charges that raise the total cost of the unit.
- We’ve completed comprehensive guides to furnaces, heat pumps, mini split heat pumps and boilers that allow you to compare costs. Use our Search Box to find the type of heat system you want to compare with an OWB.
- Work required: Even if you buy wood and the seller stacks it for you (at extra cost), you will still have to load the furnace every 10 hours to 3-4 days depending on its capacity. Adding backup gas or oil to the furnace eliminates concerns about the fire going out while you’re away, but increases your equipment cost by $800 or more.
Summary of Outdoor Wood Boiler Pros and Cons
- Reduce or eliminate heating and hot water costs
- Keep your home warmer and still pay lower energy costs
- Heat your home and other locations
- Outdoor wood boilers connect to an indoor boiler or forced air systems
- Gasification furnaces produce much lower emissions
- Fuel used reduces fuel for forest fires
- The high cost of the equipment
- The furnace needs to be fed regularly, or a backup fuel source must be added
Cost of Heating with Wood
What’s a cord of wood? A cord is a stack of wood 4’ wide, 4’ high and 8’ long. That’s 128 cubic feet. The price of a cord of hardwood varies from $175 where it is abundant to $400 where it is scarce. Local cost of living affects cost too.
Avoid face cords: If you buy wood, buy it by the full cord. A “face cord” is a misleading term that means a 4’x8’ pile, but there’s no uniform understanding of the depth. You might get cheated buy face cords.
How much would will you need? You’ll need one to five cords of wood per season, depending on where you live and whether you are heating just your home or multiple locations. If you’ve got a large home and you’re also heating the garage, a pole building and the hot tub, you’ll need more than five cords. Regardless, when comparing what you’re paying for gas or oil with what you’re paying for wood to heat the same things, wood is 50% or cheaper.
Comparing Ave. Annual Heating Cost
|Heat Type||Warm Climate||Moderate Climate||Cold Climate|
|Gas Boiler or Furnace||$340-$490||$700-$955||$1,675-$2,125|
|Oil Boiler or Furnace||$420-$565||$880-$1,130||$2,060-$2,600|
Efficiency Maine administrates efficiency programs for the state. It has put together a cost comparison calculator that with adjustable costs, so you can directly compare prices based on local energy costs in your area.
Choose the “See Details” box to change the cost or amount of fuel or the efficiency level of the device used for heating.
Top 3 Outdoor Wood Boiler Brands
These brands are the best-selling, feature-rich outdoor furnace brands in the United States. Each makes OWBs certified by the EPA for residential heating.
The company is based in Minnesota and has made outdoor furnaces since 1984. Central Boiler makes 3 residential boiler lines plus the Classic commercial line and Forge, a coal-burning series. See our Buying guide of Central Boiler wood furnace to check the latest prices and reviews of different Central Boiler models and avoid getting Ripped Off!
The residential lines are:
- Classic Edge wood furnaces: Three boilers from 150 to 330 gallons and fire boxes from 10 to 24 cubic feet. BTU range is 170,000 to 240,000.
- E-Classic wood furnaces: Two boilers, a 200-gallon, 200,000 BTU model and a 410-gallon unit that makes 245,000 BTU.
- Maxim pellet and corn furnace: This is a 90-gallon model with an 11-bushel hopper and other accessories.
- GS Series wood furnaces: Three units range from 120,000 to 340,000 BTU with water capacities from 90-260 gallons.
- G Series wood furnaces: Three furnaces are basically the same as the GS Series, but they have additional performance features and can be installed indoors too.
- MF eSeries: The five models in this series burn either wood or coal. Capacities range from 60 gallons and 150,000 BTU to 555 gallons and 800,000 BTUs. There’s a unit for homes and buildings of almost any size.
- C Series: These OWBs burn coal. The capacity range is the same as the MF eSeries furnaces.
Heat Master offers stainless steel fireboxes on most series, though at significant additional cost. The brand also makes the B Series corn/pellet biomass furnace for commercial applications. See our Buying guide of Heat Master wood furnace to check the latest prices and reviews of different Heat Master models and avoid getting Ripped Off!
Crown Royal Stoves
Crown Royal makes 2 boiler series for residential use.
Pristine Gasification Series wood furnaces: The three models in this series range from 190 gallons and 125,000 BTU to 290 gallons and 390,000 BTU. These are high-efficiency furnaces reduced emissions.
Shaker Grate Series coal furnace: This single-size coal boiler has 380-gallon capacity and creates 365,000 BTU.
The company also makes an indoor wood boiler series and a commercial biomass series.
See our Buying guide of Crown Royal Stoves wood furnace to check the latest prices and reviews of different Crown Royal Stoves models and avoid getting Ripped Off!
Tips for Buying an Outdoor Wood Boiler
Most local dealers have a store where you can see the equipment and learn about it from an experienced salesperson. They should be able to assist you in assessing your heating needs and help you choose a furnace that meets those needs.
We always recommend shopping around. Visit the manufacturer websites too where you can learn more about the outdoor furnaces. Most sites have videos explaining the boilers, how they function, installation information and much more.
Properly sizing your OWB is crucial, and an expert can help you select the right size. Obviously, it needs to have enough water and BTU capacity to accomplish your heating purposes. However, if it is too large, it will smolder because the dampers will be closed much of the time. Smoldering means smoke and wasted fuel.
The more lead time you have before purchasing the boiler, the more you can learn – and the better decision you’ll make.