Condensing Vs. Non-Condensing Boiler: What’s the Difference?


Many homeowners often compare condensing vs. non-condensing boilers when setting up a central heating system. But it’s one of the few choices you must address when replacing or installing a new boiler.

So, chances are you have a non-condensing boiler if your house uses an old boiler or furnace system. Hence, upgrading may mean switching to a condensing model. However, an upgrade won’t be possible if you don’t understand how they work.

We’ll discuss how these heating systems work and compare them to extract the differences.

Are you ready? Let’s begin!

How do Non-Condensing Boilers Work?

Boiler room with different equipment

Boiler room with different equipment

Non-condensing boilers follow the standard boiler process. But they distribute their waste as fumes. These fumes travel through the flue, which sends them outdoors.  

Also, these fumes are hot vapors that retain some energy from the gas powering the boiler.

As a result, non-condensing systems waste energy when they allow heat to escape via fumes. But, these systems are more widespread than their condensing counterparts because they have lesser parts and simple designs.

Further, boilers with non-condensing systems are cheaper and require less maintenance.

How do Condensing Boilers Work?

Boiler in a tiled room

Boiler in a tiled room

Condensing boilers don’t let the heated fumes escape outside. Instead, they have extra components and features allowing them to extract heat from the vapor for saving and recycling. Hence, these boilers have higher energy efficiency.

Moreover, the additional parts include one large heat exchanger surface or double heat exchangers. Condensing boilers recover energy from superheated vapors traveling through the heat exchanger.

Then, the heat exchanger cools the vapor to a dewpoint temperature before condensing it into a corrosive liquid. However, the condensation process stays within the walls of the boiler, ensuring it doesn’t have contact with anything outside the system.

Further, condensing boilers have internal high-grade stainless steel walls preventing damage from corrosion. 

Condensing Vs. Non-Condensing Boilers: The Differences

Condensing boilers have unique functions, making them different from non-condensing variants. Let’s compare and explore these differences:

Environmental Friendliness

In truth, boilers are not environmentally friendly, regardless of the type (gas or electric). And the fumes flowing through the flue contain high carbon dioxide levels, which is harmful to the planet.

However, condensing boilers capture most CO2-filled vapor and recycle it as a secondary heat source. Hence, these boilers release less harmful gasses into the atmosphere, making them energy efficient.


Man installing boiler unit

Man installing boiler unit

Condensing boilers have expensive price tags, which most people avoid because of the expenses. But it’s costly because this system has more parts, high-quality materials, and more complicated components.

Moreover, condensing boilers compensate for this pricy upfront cost with high energy bill savings. No doubt, condensing systems offer nothing less than 90% efficiency. 

In contrast, conventional boilers have fewer components and parts, making them less expensive and easier to operate. But, they won’t offer benefits you’d get from their condensing counterparts.

Energy Efficiency

Multiple boiler units in a room

Multiple boiler units in a room

You can find boilers with different energy sources, including gas, oil, or electricity. However, condensing boilers have more efficient energy consumption than other boiler types. Undoubtedly, this high energy efficiency will reflect on your monthly power bills, allowing you to save money while maintaining your home’s heat level.

Although each boiler type offers different efficiency percentages, you can enjoy 15% more energy savings with condensing boilers. On the other hand, conventional boilers provide 75% efficiency, which is low compared to the 90%+ of condensing systems.

Moreover, older non-condensing systems may operate at 50% efficiency. Hence, an upgrade to condensers may provide up to 50% energy savings. Therefore, condensing boilers are the go-to if long-term efficiency is your goal.


Man giving a thumbs up near a boiler

Man giving a thumbs up near a boiler

While demands for condensing boilers are increasing, they’re still not popular enough to replace non-condensing systems. Plus, you may find it challenging to employ local HVAC companies selling, installing, and servicing condensing boilers.

In addition, condensing systems are new technologies that require extra expertise to handle. Fortunately, they’ll become cheaper eventually and make their way to several homes, forcing companies to adapt & offer these services.

Non-condensing boilers are affordable but will soon be out of commission. Governments are raising energy efficiency standards, and we expect conventional boilers to fall behind, giving condensers more room to become widespread.

Maintenance and Installation

A woman calling for boiler maintenance

A woman calling for boiler maintenance

No doubt, condensing boilers have more components and complex designs. For this reason, most technicians find them challenging to install. Unfortunately, this also makes them expensive.

On the other hand, non-condensing boilers have been around for decades. So they’re easier to install and maintain. Additionally, setting up a condensing system from scratch requires some tweaks and additions to your auxiliary system.

Also, maintaining condensers can be a hassle. All parts and components require cleaning and maintenance, making the process hectic and expensive.


Do condensing and non-condensing boilers have different installation processes?

Yes. Non-condensing units have direct access to standard chimney vents. But condensing systems require materials that can handle the corrosive liquid of these boilers. Thus, you’ll need venting materials like PVC, polypropylene, or CPVC.

Can you control a condensing boiler’s corrosive liquid?

Condensing boilers have stainless steel heat exchangers capable of handling corrosive condensate without fail. Also, these units are void of heat exchanger materials like cast iron and copper, commonly found in non-condensing units.

Final Words

Condensing and non-condensing boiler systems offer different benefits discussed in this article. Generally, condensing units are better options since they consume less fuel and produce lower carbon footprints.

But the ideal boiler for you depends on your needs and budget. For example, condensing boilers may cost between $10,000 to $15,000, while non-condensing units will cost way lower ($8000 to $12,000). However, various factors determine your installation cost, like home & boiler size, number of zones, and amount of necessary adjustments.

In addition, non-condensing units often have longer lifespans and lesser maintenance costs.

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