How to Buy a Coal Furnace

In recent years fuel prices have fluctuated greatly, causing many people to seek out alternative ways of supplying heat and hot water to their homes. One heating alternative that seems to be growing in popularity is outdoor coal furnaces. But because they are still not as widely known or used as oil- and gas-fired boilers and furnaces, information about coal furnaces is not as easy to come by.

Issues to Consider

You want to choose the right heat source for your home, especially on those cold winter nights. Important information to know about coal furnaces includes:

  1. Why purchase a coal furnace instead of a wood furnace?
  2. Types of coal
  3. Pros and cons of a coal furnace
  4. Determining size and cost
  5. Is an outdoor coal furnace compatible with my existing heating system?
  6. How long does a coal furnace last?
  7. Who installs and services coal furnaces?

Why purchase a coal furnace?

Most outdoor wood furnace companies now sell a combination of wood and coal furnaces, and in many cases only coal furnaces. This is because of Environmental Protection Agency (EPA) clean air standards updates for wood furnaces designed to improve air quality in areas where wood is burned for heat.

Until 2015, wood furnaces were only regulated on the state level, meaning individual states could have different laws regarding their installation and use. Concerns over the health and environmental impact of wood smoke initiated EPA regulation of wood furnaces at the federal level. The new regulations requires that wood furnaces meet emission limits in two steps: Step 1, which became effective in 2016, requires an emissions limit of 0.93 pounds of PM per million Btu heat output; Step 2, which must be met by 2020, requires an emissions limit of 0.15 pounds of PM per million Btu heat output for each individual burn rate.

Coal furnaces are not covered by EPA requirements and can be sold without regulation as long as they don’t advertise that they can also burn wood. For this reason, as well as the relatively low cost of coal, outdoor coal furnaces have increased in popularity among both manufacturers and consumers.

Types of coal

The two main types of coal used are Anthracite and Bituminous. Bituminous coal, also known as soft coal, burns easily, requiring lower combustion temperatures than Anthracite with a greater percent of fixed carbon and greater heat value. However, it also releases smoke containing sulfur dioxide and other pollutants as it burns. This coal was burned for the past century or so and allowed contaminants into the air, making it bad for the environment. We’ve all seen pictures of coal-fired factories with smoke stacks billowing black smoke, or coal miners covered in black dust. That’s Bituminous coal. Bituminous coal should not be used in an outdoor coal furnace.

Anthracite, also known as hard coal, is a very clean source of fuel and produces almost no smoke or emissions. Anthracite coal is very low in sulfur content compared to cord wood and other fossil fuels. It is more difficult to fire up and requires higher combustion temperatures, but because of its far lower emissions Anthracite is the only coal that should be used in an outdoor coal furnace.

Finding Anthracite coal to burn used to be a concern with coal furnaces. However, with the increased interest in renewable and alternative fuels in recent years, finding Anthracite to burn should no longer pose a problem. Some outdoor coal furnace manufacturers sell Anthracite coal to use in their furnaces, and hundreds of Anthracite dealers are available, with most located in the northern states. These dealers can be found on Anthracite dealer location websites.

Pros and cons of an outdoor coal furnace

Heating with coal has its benefits and drawbacks. Here are a few to consider:


  • Coal can be less expensive than gas or oil
  • Anthracite burns clean, without the smoke or smell of wood
  • Unlike wood, it does not require much storage area
  • Easier to load than wood
  • Outdoor coal furnaces are located away from the house, reducing fire risk
  • Can heat a home with no chimney


  • The biggest drawback is having to feed the boiler every 12 hours or so. Besides the work involved, this also requires a clear pathway to the furnace in all weather.
  • Approximately 5 to 10 pounds of ash is produced for every 50 pounds of coal burned, requiring regular cleaning of the ash pan.
  • The furnace will require regular maintenance, including oiling door hinges and inspecting and clearing the vent of blockages.

Find a Certified Heating & Cooling Professional In Your Area

Contact a top-rated local expert to help with all of your home’s HVAC needs.

Determining size and cost of a coal furnace

The most important factor when determining the size of coal furnace necessary for your home or building is BTU usage. Factors that can affect this include square footage of the home, how well the home is insulated, and the climate where you are located. When it comes to coal furnaces, most manufacturers believe it is better to be a little oversized than undersized. It is important to work with the dealer or manufacturer to do an estimate of BTU usage before purchasing a furnace.

The cost of an outdoor coal furnace depends largely on the size of the unit, measured in BTU capacity and the size of the water tank, along with the manufacturer brand. Coal furnaces generally range in price from around $3,000 for smaller units to over $10,000 for larger furnaces. Delivery costs are usually included in the price. Installation costs are sometimes included, but you should check with your local dealer or the manufacturer to make sure.

Is an outdoor coal furnace compatible with my existing heating system?

Coal furnaces are designed to work with an existing heating system. Water-to-air or water-to-water heat exchangers or direct circulation carries the heat into the home or building’s forced-air furnace, radiant baseboard or radiant floor heating system. This allows you to use an existing thermostat control. Coal furnaces can be used for domestic hot water as well as heat.

You may also want to know how a coal furnace works.

How long does a coal furnace last?

Coal furnaces are expected to last at least 20 years, and most coal furnace manufacturers have warranties between 20 and 25 years on these products. There are several criteria which manufacturers require to prevent voiding the warranty. These usually include regular maintenance of the unit, submitting water tests and using a water treatment annually. Burning wood in a coal furnace will automatically void the warranty from almost every manufacturer.

Coal furnace installation and maintenance

Coal furnaces are usually installed by qualified professional dealers who are trained by the manufacturer.

Unlike a furnace or boiler fueled by gas or oil, technicians who install and service coal furnaces are few and far between. The good news is that, unlike modern gas and oil furnaces, outdoor coal furnaces are uncomplicated units, designed so that even a novice user can usually work on it. If a serious problem does arise, your local dealer or the furnace manufacturer will need to be contacted.

HVAC Brands

Learn more about your home's heating and cooling system with our guides, how-to's, FAQ's, tips and more.

Ready to get a quote from an HVAC contractor?

Let us know what type of service you need and we can connect you with a certified local HVAC contractor.

Please enter a valid name

Please enter a valid phone number

Please enter a valid zip code

There are no dealers in this zip code.

Please enter a valid email address

Please select repair or replace

Please select heating, cooling or both