Boiler vs. Furnace: What Are the Differences?
Which option represents the height of home heating?
Highlights
Boilers circulate hot water or steam to heat homes.
Furnaces blow hot air through ducts.
There are many options for both boilers and furnaces.
Boilers can be easier to maintain.
Furnaces are more affordable to install.
There’s nothing quite like snuggling with your favorite blanket and a cup of hot chocolate on a cold, wintery day. For this luxury, you can thank your heating system. Most homes have either a boiler or a furnace, and both do a great job of keeping you warm and toasty all season long.
But wait—is a boiler a furnace? Actually, no. Despite their similar end goals, the two systems are quite different. To settle the boiler versus furnace debate, we analyzed the differences in cost, functionality, system setup, and more to help make your decision a little easier.
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Boiler Pros and Cons
Boilers circulate hot water or steam through radiators and radiant floor heating to heat your home. Some people prefer the way boiler heating feels, and they usually cost less to run—who would say no to a lower utility bill?
Pros
Distributes heat evenly
Doesn’t blow allergens or dust in the air
Runs more quietly
Provides hot water to your faucets
Cons
Expensive to install
Requires more maintenance
Condensate pipes can freeze in extreme temperatures
How a Boiler Works
Boilers work by transferring heat to water or steam. When it’s hot enough, that water or steam distributes throughout your home. Here’s a bit more into how boilers work:
When your thermostat detects a drop in temperature, the boiler powers on using oil, gas, or electricity.
The water inside your boiler heats up until it’s hot enough to travel through your home using a radiator or baseboard heater system to warm the rooms.
When the water cools down, or the steam condenses, it goes straight back to the boiler to be reheated.
This cycle repeats until your home arrives at the temperature set on your thermostat.
Once this happens, the boiler turns off until the temperature drops again.
Furnace Pros and Cons
Furnaces heat your home by delivering hot air through ducts, which is handy because it uses the same ducts for your air conditioning in the summer. They’re a popular choice for new builds—according to the National Association of Home Builders, almost 99% of new single-family homes built in 2020 have a heat pump system or a furnace.
Pros
Costs less to install
Takes up less space
Warms the home up faster
Provides reliable heat even in the coldest months
Cons
Can dry out the air
Operation is noisier
You need to replace air filters regularly
Gas furnaces risk carbon monoxide poisoning, line leaks, and fires if not maintained properly.
How a Furnace Works
A furnace operates differently than a boiler in that it uses hot air to distribute heat through a duct system. While some furnaces—like a ductless heat pump—operate using a radiator or baseboard heating similar to a boiler, all furnaces use air to transfer heat throughout the home. Here’s how:
When your thermostat drops below the desired temperature, your electric or gas furnace kicks in to generate heat through combustion.
The flames in your furnace’s burner heat the air, which then travels to a heat exchanger.
From there, the heated air is forced through a vent and sent through the exhaust pipe.
A blower fan pushes the warm air through the duct system in your house, distributing heat and redirecting cold air to the furnace.
When the thermostat detects the desired indoor air temperature, the gas valve switches off.
Boiler vs. Furnace: Which Is Right for You?
Both boilers and furnaces can do a great job heating your home in the colder months. If you’re having difficulty deciding between the two, you can narrow it down by considering your budget, timeline to install a system, fuel options, and more. You may also reach out to a local furnace installer or boiler installer for more detailed and specific information.
Fuel Source
Both boilers and furnaces have models that use electricity, natural gas, propane, oil, or wood pellets. The only difference is that wood pellet furnaces are only available for outdoor use, and wood pellet boilers offer indoor heat.
In particular, electric heating options appeal to homeowners because they don’t require access to natural gas pipelines, and they don’t require refuelings like propane, oil, or wood models.
If you feel drawn to boilers, you can choose from a standard model with one tank for cold water storage and a cylinder for hot water or a combination model that heats water on demand with no need for a storage tank.
In addition to gas or electric furnaces, you can also consider a ductless mini-split furnace that you can install anywhere with minimal invasion.
Most options: Tie
Price
The average cost of a boiler is $5,900 plus $1,000 to $3,000 for installation. If you opt for a high-efficiency boiler, the unit price increases from $6,000 to $11,000.
The cost of a new furnace unit is around $2,800 to $6,800. The most affordable furnaces are electric and mini-splits, which cost $2,000 to $15,000. Gas furnaces cost $3,800 to $10,000. Installation labor will run you $150 to $500 per hour.
Most affordable: Furnace
Ease of Installation
Generally speaking, both boilers and furnaces require professional installation. Many steps are involved in installing or replacing a unit, from removing the old unit to preparation, installation, and system testing. And if you want the benefits of being covered by an installation warranty, it needs to be done by a seasoned HVAC pro.
Installing a boiler is much more labor-intensive than installing a furnace. From setting up the boiler room, installing pipes, and connecting the gas lines, installation can take up to three days. On the other hand, a pro can complete a furnace installation in one day.
Easiest Install: Furnace
Ease of Repair
Most boiler issues will require you to call an HVAC professional because the parts are complex. Common problems may include leaks, emissions issues, and temperature problems—the cost of a boiler repair averages between $240 and $2,500.
Furnaces are better suited for DIY repairs like resetting your circuit breaker, replacing a clogged filter, or installing a new safety switch. If you discover that the problem is too complicated for you to handle on your own, calling in a pro for furnace repair costs $130 and $1,200.
Easiest to repair: Furnace
Maintenance
When comparing forced air versus boilers, maintenance is an important factor for keeping both systems in good shape. Boilers require an annual inspection by a certified tech. Many also recommend flushing the boiler, lubricating the pumps twice a year, and checking for leaks every month.
Furnaces also require an annual inspection and cleaning. Your tech will check carbon monoxide levels, gas lines, flame sensors, and more. If you’re an experienced DIYer, you might also take on the cleaning yourself. And every one to three months, you should change the furnace filter.
Easiest to maintain: Boiler
Length of Life
Boilers can last 10 to 25 years with proper maintenance. As they experience general wear and tear, you may notice water leaks, longer heat times, and odd noises that indicate part failure.
Electric furnaces last 20 to 30 years, and gas furnaces last 15 to 20 years. Towards the end of its lifespan, you may notice signs to replace or repair your furnace, including uneven heating or cooling, high carbon monoxide levels, and loud rattling.
Longest lifespan: Furnace
Eco-Friendliness
How sustainable boilers or furnaces are depends on the type and the manufacturer. For example, combination boilers are more eco-friendly than others because they emit less nitrogen oxide. Boilers fueled by wood pellets are also considered carbon-neutral.
The general consensus is that electric boilers and furnaces are more eco-friendly. You can also opt for high-efficiency models that use less energy for either heating type, which will lower your utility bills.
Most eco-friendly: Tie
Climate
Boilers might not be the best choice for homes in warmer climates, as in those places, you’ll likely want an all-in-one HVAC system that comes with an air conditioner and furnace. However, boilers are a great choice for homes in cooler climates because of their consistent heat flow, which warms the room evenly.
Keep in mind that some homeowners in warmer climates might still opt for a boiler for a number of reasons: Boilers are quieter and more suitable for homes where air quality really matters. Since furnaces push air throughout the home, they also may be more prone to spreading air pollutants, which can be a dealbreaker for those with allergies or asthma.
Best for cold climates: Boiler
Allie Ogletree contributed to his piece.
Frequently Asked Questions
Today’s boilers and furnaces are pretty safe and typically include safety switches and sensors to protect you from risk of fires or combustion gas leaks. However, boilers are typically considered safer than furnaces because they pose less of a fire risk. The bigger risk with boiler systems is water leaks.
People are getting rid of boilers because of new and potential legislation in countries around the world that phase out or will phase out certain types of boilers. For instance, the U.K. government has announced it will begin banning installation of gas boilers in newly constructed homes starting in 2025. The reason for this ban is to promote alternative fuel sources with less environmental impact.
The common types of boilers include conventional boilers, system boilers, combination boilers, or high-efficiency boilers. Conventional boilers have a large hot water storage cylinder and a cold water tank. Similarly, a system boiler has a cylinder to provide instant hot water throughout the home. Combination boilers do not have the additional storage. High-efficiency, or condensing, boilers draw heat from combustion to operate more efficiently.
The different types of furnaces include electric, natural gas, propane, oil, and wood. Furnace types vary based on the fuel source, and there are benefits and drawbacks to each. While electric furnaces tend to cost the least upfront, they have higher utility costs. Wood furnaces tend to be the least expensive to operate and don’t rely on utilities, but they can be expensive upfront and require a lot of regular cleanings and tune-ups.