Tools and Knowledge Base

Energy Independence

For over 35 years, Alternate Heating Systems solid-fuel heating appliances have provided homeowners with energy independence by offering high-quality, long-lasting solid-fuel home heating options. By choosing to heat your home with an AHS Wood/Coal Boiler and domestically-produced solid-fuel, you are choosing energy independence! AHS Wood/Coal Boilers are designed to be used independently or as an add-on to your existing hydronic heating system, and burn either air-dried wood, or anthracite coal in buckwheat or Pea sizes.

Safety and Reliability

All AHS Wood/Coal Boilers are constructed of heavy 1/4" steel plate, reinforced with 3/4" steel rods and welded by experienced and certified welders to ensure safety and durability. For additional safety, a 30 PSI pressure relief valve is included with every AHS Wood/Coal Boiler. For increased longevity and performance, all Wood Gun boilers feature 3000-degree firebrick, Multi-Fuel boilers feature heavy Rolla Grates™, and all models are constructed with reinforced doors. 

Are Alternate Heating Systems boilers insulated?

The AHS Wood Gun and Coal Gun are fitted with insulation and sheet metal covers as standard equipment.  In most Multi-Fuel installations, we assume that you are installing the unit in a basement or other space that will benefit from the heat radiating from the boiler itself. The Multi-Fuel boiler is available with a sheet metal and insulation wrap, referred to as  an "insulation jacket" on our price list.

What is an updraft boiler and what is a downdraft boiler?

Updraft and downdraft refer to the way air passes through the boiler. In updraft boilers the chimney is what creates the draft and air movement through the boiler is always either sideways or up. In downdraft boilers a fan is used to create airflow and the air is actually pulled down through the boiler before exiting the boiler and going up the chimney. 

The AHS Wood Gun versus Competitors

The AHS wood gasification boiler design is superior to our competitors' in both quality and durability. There are currently AHS stainless steel Wood Gun boilers that have been in operation for over 27 years with no sign of deterioration. Our Wood Gun boilers have much longer burn cycles and operate at lower exhaust temperatures (an indicator of total efficiency) than our competitors' unit. Additionally, the Wood Gun does not require an expensive water storage system unlike some of our competitors'. Most of our competitors in the wood gasification market only focus on the residential segment. We offer an expansive product line that includes larger units aimed at the mid-level commercial market as well as the residential market. In comparison to similar offerings by our competitors, our Wood Gun boilers are competitively priced across the board. The bottom line is that the Wood Gun is less expensive and more durable than any of our competitors' products.

Alternate Heating Systems are UL and CSA approved

Currently, the Wood Gun and Coal Gun are listed under US, UL 2523-2009; UL 391-2010; UL 726-2006; CAN/CSA B366. 11-2001. These certifications may be required by some states, municipalities, or insurance companies - it is the responsibility of the customer to determine the need for ASME or UL certification on any boiler purchased. Base unit pricing does not include these certifications by default. Alternate Heating Systems Products are built and tested to ASME standards:


It is important to choose a solid-fuel heating appliance that is correctly sized for your home or business. When it comes to boilers, bigger is not always better. A slightly undersized solid-fuel boiler will generally require hot fires which burn cleaner and more efficiently than the slow-burning or smoldering fires generated in an oversized boiler.

In addition to square footage, some of the factors that may affect your heating needs are your home / buildings age, design, and geographic location (climate). Other factors to consider are your chimney’s draft strength and whether you plan to burn wood or coal as your primary fuel source. For assistance with determining which AHS heating unit is right for you, please contact a AHS sales representative for recommended sizing. You may also use our BTU Calculator.


Alternate Heating Systems Wood Gun & Coal Gun boiler vessels are backed with a 20 year limited warranty on materials and workmanship. All other components both manufactured by AHS and purchased from vendors will vary in length of warranty from 30 days to 1 year. A copy of the complete AHS warranty is available in every AHS Installation, Operation & Maintenance Manual.

Fuel Cost Comparison

Fuel Cost Calculator (external site)