Furnaces and Boilers: The Difference

Both furnaces and boilers produce and distribute heat. A boiler is a vessel that heats water and then pushes the steam or hot water through a system of pipes via radiators, baseboards, or underfloor radiant heating. A furnace forces heated air through ducts, which is why it’s sometimes called a “forced hot air” system. Keep in mind that replacing filters and cleaning ductwork on a regular basis preserves the air quality in your home or business and can extend the life of your system.

  • Wide variety of fuels: oil, gas, pellet, and cord wood
  • Zone heating: boilers let you heat only the rooms you want to
  • Use existing ductwork: furnaces integrate with air conditioning

Repair vs. Replace

Repairing or retrofitting a system to a new fuel source is possible, but the return on that investment may be lower than total replacement. We recommend replacing your system if any one of the following applies:

  • Older than 15 years
  • Has a pilot light
  • Was converted to a different fuel from its original design
  • AFUE rating is below 80% (poor energy-to-heat conversion)

Equipment Failure

If your boiler or furnace has failed, contact your fuel provider immediately. You should also contact a qualified heating system contractor, particularly if your fuel provider does not offer replacement options. Not only will an expert repair or replace your system, they can also identify the cause of failure to help you avoid recurring problems. We provide rebates for efficient heating systems and low-interest financing to cover the cost of replacement.

  • Contact your fuel provider and a qualified contractor immediately
  • Ask for an energy-efficient option that meets your needs
  • Get approved for low-cost financing within two business days


Furnaces and boilers are rated by Annual Fuel Utilization Efficiency (AFUE), calculated by dividing how well a unit converts energy to heat by the amount of fossil fuel energy it consumes over the course of a heating season. A British Thermal Unit (BTU) is the amount of energy needed to heat one pound of water by one degree Fahrenheit. Heating is typically measured by dollar cost per million BTUs (MMBTUs).

  • New units rate up to 95% AFUE, older units as low as 56%
  • A typical home uses 60 to 100 MMBTUs per year
  • Compare fuels by their cost per MMBTU: range from $15 for wood to $40 for oil

Compatible Fuels

Many homes in the US use a furnace or boiler for heat, in part because they work with so many different fuel sources. Today, the most cost-effective fuels for furnaces and boilers are natural gas and pellets. Cord wood, plentiful and cheap in Vermont, can also be a good choice if you have the storage capacity. Electric-powered heat pumps can also be very efficient. Contact us for advice on the right solution for you.

Commercial Heating

Many Vermont businesses heat with rooftop furnace units, which are uniformly rated at 82% AFUE. Integrated controls and furnace fan motors can help regulate air flow, distribution, cooling, and ventilation, letting a business use only the heat it needs, when needed. For hotels and inns, these controls often include occupancy sensors to avoid heating and cooling empty spaces. For large buildings or plants, digital combustion controls offer a wide range of optimization and savings opportunities. Contact us for more information. In general, maximizing efficiencies via control systems is far cheaper and easier than buying a new system.