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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing).
Published: October 3, 2018. Updated: April 5, 2024

Condensing vs Combi Boiler

Is a condensing boiler the same as a combi boiler?

We have a lot of queries from customers asking this question and also asking what the difference is between a combi boiler and a condensing boiler.

The first answer is no, not technically. The problem is that they cannot be directly compared. A combi boiler is a type of boiler, and ‘condensing’ is the process modern boilers use to ensure efficient heating.

This means all modern boilers, including combi boilers, are condensing boilers. These can also be system and regular (or conventional) boilers.

If your boiler has suddenly broken down after 20 years of daily use, and you’ve never had to shop around for a new boiler, we don’t blame you for being stumped. Don’t worry though, we’ve written this article to answer all of your questions.

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What is a condensing boiler?

Condensing boilers are designed to be highly efficient. They can extract additional heat from exhaust gases normally lost through the flue into the atmosphere.

This process of extracting heat from gases cools the gas down and certain parts of the gas condense into a liquid. In gas, LPG and oil boilers this is an acidic water called condensate.

Condensate must be disposed of down a drain or into a soak-away. You can read more about condensate pipes in our guide. If a pipe cannot get the liquid to drain a condensate pump can be installed.

In older non-condensing boilers, this heat would have been lost. This condensing process allows modern boilers to achieve efficiencies of over 90%.

Is my boiler a condensing boiler?

If your boiler was installed after 2005, it will be a condensing boiler as that is when the law changed. Since then, it has been a legal requirement that all new and replacement boilers in the UK are condensing. If it was installed before this, the chances are it’s a non-condensing boiler.

Is a conventional boiler the same as a combi boiler?

When most people ask if a condensing boiler is the same as a combi boiler, the chances are they actually mean to ask, is a conventional boiler the same as a combi boiler? However, the answer again is no. Both a conventional boiler and a combi boiler are types of boilers.

To add some clarity, a conventional boiler is another name for an open-vent boiler. Another name for this type of boiler is a regular boiler. This type of boiler was most commonly installed in semi-detached family homes in the UK over the past few decades.

The main difference between a conventional boiler and a combi boiler is the components utilised alongside the boiler in the heating system. A combi boiler needs no other components other than the boiler itself and the pipes connecting it. Conventional boilers, on the other hand, require a hot water cylinder and a cold water attic tank.

The third most commonly installed boiler type is a system boiler. System boilers form the middle ground between conventional boilers and combi boilers, requiring the boiler unit and a cylinder for domestic hot water (DHW) storage but not a cold water attic tank.

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The benefits of switching to a condensing boiler

Even if your older non-condensing boiler hasn’t broken down, it is still beneficial to upgrade to a modern condensing boiler. This is because older boilers suffer decreased efficiency due to thermal and mechanical stresses from continuous use causing corrosion to the internal components. 

A new boiler can provide the following benefits:

  • Efficiencies over 90% with the Viessmann Vitodens 200-W hitting 98% efficiency
  • Annual savings of up to £590 on your energy bills 
  • Boiler Plus compliant features such as load compensation, weather compensation and smart controls, all of which are designed to increase efficiency

The cost of a new boiler will depend on many factors, including the size of your home and the daily hot water demands. It will also depend on if you would like a longer warranty, one of the best boilers or the cheapest boiler you can get.

If you would like an accurate price for a fully installed boiler, answer a few questions using our quick online quote tool.

Get Your FREE Online Quote Today!
Save up to £590 PER YEAR on your heating bills.
Quote in 30 seconds. No obligation. Next Day installation.
Save up to £590 PER YEAR!
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