Functionally, the most significant difference between a furnace and a boiler is that a furnace uses air to transfer heat, and a boiler uses water. However, this seemingly innocuous difference affects everything from upfront costs, efficiency and air quality, to ongoing maintenance bills.

Read on to see the benefits and drawbacks of furnaces and boilers, and which is best for your home.

What is a furnace?

A furnace can be powered by electricity, natural gas, propane, or heating oil. This system warms your home by drawing in cool air and then transferring it to the furnace through ducts. Once the air has reached the furnace, it is filtered, heated, and pushed back into rooms of your home through the same ductwork.

What is a boiler?

Rather than using air to warm your home—as a furnace does—boilers utilize hot water, making them essentially a special-purpose water heater.

A boiler uses gas, propane, natural gas, electricity or oil, to warm the water in its tank and then pushes the water through a venting system to warm your home. Once the water has cooled down, it is sent back into the boiler to be reheated and recirculated through your home.

How do furnaces compare to boilers?

The differences in how the heat is created and distributed throughout your home mean that boilers and furnaces have unique weaknesses and strengths.

Finally, because the vents of furnaces are exposed, they pose more safety risks than boilers. Objects can slip into the vents of a furnace, which is a fire risk. It’s also possible for someone’s finger or hands to reach into the vent, which poses a risk of burns.

Which is less costly: boiler or furnace?

While weighing the pros and cons of furnaces and boilers, maybe you noticed boilers have a few more advantages than furnaces. The benefits of a boiler are reflected in the price difference: Furnaces are significantly less expensive than boilers. 

The cost of a boiler—and the subsequent installation—are anywhere from 2-3 times more expensive than the standard rates for installing and purchasing a furnace.

Installing a new furnace will cost somewhere between $1,200-5,000 depending on the fuel it runs on.  A boiler, on the other hand, can cost between $5,000 and over $8,000 depending on the fuel it runs on.

Homeowners also find savings with furnaces when they are installed with a Central Air system. By combining the two systems, homeowners don’t have to pay for extra ductwork.

When it comes to efficiency, boilers may save you a bit on your monthly energy bills if your furnace is an older model. However, with newer models, both furnaces and boilers are roughly 95% energy efficiency, which means overall savings could be a moot point in the end.

Is it easier to maintain a furnace or a boiler?

On average, both furnaces and boilers have an average lifespan of 15-20 years. By giving your system an annual inspection and regular cleanings, you can even prolong the life expectancy of your appliances.

It is important to note that furnaces usually require more maintenance from a homeowner than a boiler will. Furnaces tend to be more susceptible to breakdowns, which requires a more careful eye from homeowners to keep up on regular inspections and cleanings.

In many cases, homeowners say that apart from an annual inspection, boilers require much less attention.

Which is best for your home: boiler or furnace?

At the end of the day, selecting a furnace or boiler will often come down to budget. If you can spring for the upfront cost that a boiler requires, you can enjoy benefits like radiant floor heating, and a more even flow of air.

However, furnaces are a great option, as well. Though they have a few more drawbacks compared to their counterparts, they are still an effective way to heat your home, especially if you’re on a budget.