What is The Difference Between a Boiler and a Furnace?

In the world of home heating, there is much to learn. Many homeowners are simply not educated about their home’s heating system. Therefore, it is important to make sure that you are familiar with your own HVAC system and the various components that make it up. One such component that many people are unfamiliar with is the boiler. A boiler can be used in conjunction with a furnace in order to heat one’s home. So what is the difference between a boiler and a furnace?

Boiler and furnace, two very similar words. However, despite sharing quite a few similarities and being used in many of the same contexts, they aren’t exactly interchangeable. In this article, you’ll learn What is The Difference Between a Boiler and a Furnace.

What is a Boiler?

A boiler is an enclosed vessel that has been designed for the purpose of heating water or other liquid to generate steam. It is often used as part of a larger system (such as a steam-heating system) to produce useful mechanical energy such as rotational motion or electricity. A boiler is different from a furnace because it uses external flames rather than heated materials contained within itself to heat up the water or other liquid inside.

What is a Furnace?

Furnace refers to any enclosure with an airtight compartment (typically made of metal) built around an internal combustion space and main flue gas passages. A furnace is different from a boiler because it uses the heated air inside itself to heat up its surroundings rather than external flames or other sources of outside heating elements.

What is the difference between a boiler and a furnace?

The two are very similar in that they both rely on the process of controlled combustion to generate heat, which in turn produces steam, water vapor, or hot air depending on what they’re being used for. However, they differ in how this process happens and where their energy comes from (which is why one can’t be called another).

Pros n Cons of Boilers:


  1. Even though they take up a lot of space, boilers are much more efficient than furnaces because the water inside them is well insulated and doesn’t suffer from exposure to any cold or cool air that might be in the way (which would lessen the amount of energy needed to heat it). Also, combustion happens at constant pressure so there are no pressure fluctuations.
  2. Boilers can be used for anything from providing heat to cooking food to running steam locomotives, which is pretty convenient since they’re all-purpose machines that take up a lot of space but have many different uses. 
  3. They typically have a fixed thermal efficiency (not including external losses), so there’s a good guarantee that the energy you put in will be turned into useful work.


  1. Since they’re used to transmit thermal energy from one location to another, boilers have a lot of resistance as heat travels through them and loses some of its potential as it does so. In addition, low water levels and steam leaks can lead to safety hazards and even explosions during operation.
  2. They’re not very good at managing heat or distributing it evenly, making them inefficient for tasks that require a lot of precision (such as powering turbines). This is because they take up too much space for the amount of energy they produce, which limits the power output you can get out of them.
  3. It’s also difficult for these machines to switch between different tasks, which means that it’s usually not worth the cost to install multiple boilers (which can be prohibitively expensive).

Pros n Cons of Furnace:


  1. Furnaces are much better at distributing heat evenly, so they’re a lot more efficient for tasks that require precision (such as heating homes). They can also provide more even temperatures across different parts of the room, making them appropriate for uses where some parts of the surroundings might get too hot while others remain cold.
  2. It’s much easier to control the amount of heat a furnace is able to produce, which means they can be used for tasks that require very specific amounts of power. Also, they’re capable of handling high pressure levels without becoming unstable, making them safer and more reliable than boilers at high efficiencies.
  3. Furnaces are much smaller than boilers, so they can be used in situations where there’s not enough space to accommodate the latter.


  1. They’re much less efficient than boilers because their energy is generated through open flames instead of constant pressure combustion, which means that a lot more heat escapes into the surroundings instead of staying inside to do work. Also, their high temperatures can be pretty dangerous to anyone who comes into contact with them, making it easy for them to cause fires and serious injuries.
  2. Furnaces are difficult to control because the rate of combustion is constantly changing, which makes it very difficult to know how much energy they’re generating or what kind of work they might be doing at any given time.
  3. They’re much less reliable than boilers because they’re constantly exposed to cool air, which makes their materials more liable to break down over time. Also, even the best furnaces tend to have a lot of pressure fluctuations during operation, which means that it’s difficult to guarantee the amount of energy they produce at any given time.
  4. Open flame furnaces can also be very costly to operate because there’s always a lot of fuel that gets burned as the flames help generate energy, which means that they’re not as viable for tasks that require a long-term investment of energy (such as heating homes).

Boiler vs Furnace – Which one to Choose?

So which one should you choose? Here are some things to consider that will help you decide:

How big is your house? If it’s small (under 1,500 square feet), a furnace will be more than enough to keep it warm. A boiler, on the other hand, may be overkill for such a small space.

What’s your budget like? A furnace can cost as little as $2,000 while a boiler can cost upwards of $6,000. However, you’ll want to factor in the cost of maintenance as well—boilers require more upkeep than furnaces do.

Where are you located? Boilers are better for areas that get cold in the winter because they can run even when temperatures drop.

In general, boilers are better for tasks that require a lot of power and very little precision (such as powering locomotives), while furnaces are better for tasks that require precision but not a lot of heat or energy (such as heating homes).

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