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Last updated: 24 March 2022

Condensing vs. Non-Condensing Boilers

What Are the Differences Between Condensing and Non-Condensing Boilers?

The main difference is that condensing boilers are up to 99% efficient while non-condensing boiler are only up to 78% efficient. This means that condensing boilers help you save up to £310 per year on gas bills while also reducing your household emissions.

If you want to replace your old boilers and you are looking into upgrading to a different model, you should know by now that it is required by law to install condensing boilers when you change your current ones. 

Differences between Condensing & Non-Condensing Boilers
Condensing Boilers Non-Condensing Boilers
One or more larger heat exchangers Single combustion chamber
and single heat exchanger
Lower temperature of combustion
products (around 55°C)
Higher temperature of combustion
products (around 180°C)
Exhaust gas is recycled through the
condensing heat exchanger
Combustion gases go into the flue and
30% of the heat is wasted
Help combat climate change
by reducing CO2 emissions
Higher carbon footprint
Higher initial cost, but
cost efficient in the long-run
Lower initial cost, but
very costly venting

What Are the Advantages of Condensing Boilers?

There are many advantages associated to condensing boilers that make them a better alternative to
non-condensing ones. The most important upsides are:

Increased Energy Efficiency

The main reason why condensing boilers are better than non-condensing models is that they are at least 25% more efficient. Their level of efficiency is achieved by using waste heat in flue gas to preheat the cold water entering the boiler, capturing more heat from the outside rather than the inside of a room. Hence, condensing boilers capture up to 11% more heat than non-condensing boilers. By reaching up to 99% efficiency, condensing boilers can help you lower your fuel bills significantly and reduce your carbon footprint, making them a great alternative heating system.

While newer non-condensing boilers can reach up to 78% efficiency (which is the percentage of heat that is actually usable), old ones usually do not reach over 55-65% efficiency. The higher efficiency of condensing boilers results in savings of up to £310 per year, according to the Energy Saving Trust.

Condensing Boilers Efficiency Chart

Lower Carbon Footprint

Since 2005, it has become mandatory to install condensing boilers if your old boiler needs replacing. Condensing boilers significantly reduce carbon emissions and you can save up to 1,200 kg of carbon a year by installing one in your home. This makes condensing boilers eligible for grants under the Green Deal, which can help you cover the installation costs.

Safer for Your Home

Because condensing boilers are perfectly sealed for heat insulation, and capture air directly from the outside of the room they are placed in, there is no risk of anything being sucked into the boiler. Furthermore, there is also no risk of being in contact with toxic substances as the condensed liquid is disposed of via a pipe connected to the drainage system.

Moreover, condensing combi boilers are more space-efficient since they do not need a water tank and can be stored in a kitchen cupboard.

What Are the Disadvantages of Condensing Boilers?

It is argued that a perfectly functioning traditional boiler shouldn’t be replaced until it no longer works. This is due to the few disadvantages of condensing boilers.

More Complex Systems

First of all, the system can shut down in very cold weather because the external pipe (which is absent in non-condensing boilers) is susceptible to freezing. Moreover, condensing boilers can start to become corroded by the acid condensate. However, because of the efficiency gain, condensing boilers are still very much worth it.

You should definitely consider keeping your old boilers if they still work at full efficiency, but switching to condensing boilers is advisable once the efficiency levels drop and it is economically inconvenient to keep servicing the old model.

More Expensive to Maintain

Condensing boilers are more expensive to maintain due to the complexity of the systems, which can affect gas boiler prices. Non-condensing boilers are cheaper to fix and they might save you some money in the short-run. However, condensing boilers are the most beneficial option in the long-run.

Condensing Boilers Long-Term Efficiency

How to Choose the Condensing Boiler That Fits You Best?

There are numerous factors that need to be considered when switching to a new boiling system. To make your choice easier, information regarding boiler manufacturers and types of boilers (electric-combi boilers, gas boilers, oil-fired boilers, wood-pellet etc.) available in the UK are provided to you. 

For customised information, you can always request a quote and you will be provided with up to 4 boiler producers that best fit your needs. It is obligation-free and does not cost anything. Simply fill in the contact form at the top of the page.

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