Differences Between Furnace and Boiler Systems

Minnesota winters make reliable heating a must. Understand key differences between furnace boiler systems and choose the best option for your home.

Minnesota winters make reliable heating a must. Does your home have a furnace or a boiler?  Each has pros and cons. To help you choose the best option for your home, we’ve outlined five key differences between furnace and boiler systems.

Heat Source and Circulation

The main distinction between the two is how they produce and distribute heat. Simply put, furnaces use warm air to heat the home while boilers use warm water, which is called a “hydronic system.”

A furnace uses a device called a heat exchanger to warm the air, which is then circulated throughout the home via ducts and blower fans. In a boiler system, water is heated within a tank and distributed through pipes to different end points in the home, typically baseboard heaters or radiators.

Maintenance and Lifespan

Generally, furnaces require more maintenance and tend to have a shorter lifespan compared to boilers. With a boiler system, excess air created through the water-heating process needs to be bled regularly. Essentially, this means emptying extra air from the system to maintain proper pressure and thus safe, reliable heating. The frequency varies from system to system. And since the system uses water, it is possible for pipes to freeze in extreme temperatures.

For optimal air quality with a furnace, the air filter should be replaced every one to three months if disposable, or cleaned monthly if re-usable. Ductwork will need professional cleaning every three to five years, and preventative maintenance from an HVAC specialist is recommended before each heating season to help avoid costly repairs.

Energy Efficiency

Furnaces can heat a home more quickly, but boiler systems are known for better efficiency. They’re a closed-loop system: The hot water circulated throughout the home returns to the tank to be re-used, now requiring less time/energy to boil as it’s already fairly hot.

Boilers also allow you to only heat specific areas of the home, resulting in lower energy bills. High-efficiency furnaces offering 90% or more annual fuel utilization efficiency (AFUE) are available, meaning 10% or less of the energy produced is expelled as exhaust. However, these furnaces are trickier (and thus more expensive) to install as they need to pull in air from the outdoors to operate.

Air Quality

The ductwork used by furnaces can accumulate dust, dirt, and other allergens that affect your home’s air quality. Boiler systems avoid this issue by circulating hot water through pipes that then radiate heat. Humidity is a natural byproduct of the boiler’s hydronic system, however, and may require dehumidifying for safety and comfort.


As mentioned earlier, boilers tend to have lower operating costs and can help save on energy bills. However, initial costs including unit and installation can be two to three times higher for a boiler. Furnace installation is more common and tends to be quicker and easier, especially if ductwork is already in place for a central air system.

There isn’t a single right answer for home heating solutions. Understanding the differences between furnace and boiler systems is important for choosing the right one for you, and the experts at Stafford Home Service are here to help! Schedule an inspection today, and contact us for all your HVAC needs.

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