condensing or 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 answer to the first question is no. The answer to the second question is that there are many differences because a combi boiler is a type of boiler, whilst a condensing boiler refers to the process a boiler utilises to increase efficiency. All combi boilers installed in the UK now must be condensing boilers but not all condensing boilers are combi boilers, these can also be system and regular 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 at the moment and confusing combi boilers with condensing boilers. Don’t worry though, we’ve written this article to answer all of your questions.

Looking to switch to a 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 that 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 into 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.

If your boiler was installed after 2007, 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.

All of the gas and oil boilers you can buy in the UK in 2021 must be condensing.

Combi is short for combination boiler. A combi boiler is called this because it combines the components for heating and hot water in one unit. With a combi boiler, you don’t need a separate DHW storage cylinder or an attic tank. 

A combi boiler has a primary heat exchanger for heating and a secondary plate heat exchanger for hot water.  A basic combi boiler will suffice if your property has 1-2 bedrooms and 1 bathroom and there is no simultaneous hot water requirement from multiple taps.  Even if your property is larger than that and you need on-demand hot water from multiple taps simultaneously, there are larger capacity combi boilers and storage combi boilers available too.

Further reading about combi boilers

Condensing boilers are gas and oil boilers that are designed to be highly efficient by condensing water vapor in the exhaust gases and recovering the latent heat in these using vaporisation.

These exhaust gases, which are mostly hot steam with some acidic content, are passed through a heat exchanger first to recover any heat contained within them. The condensed vapour then leaves the system in liquid form via a drain.

In older non-condensing boilers, this heat would have been lost. It is this condensing process that allows condensing boilers to be able to achieve efficiencies of over 90%.

The benefits of switching to a condensing boiler

Even if your older non-condensing boiler hasn’t broken down, it is still beneficial to switch 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 condensing boiler can provide the following benefits:

  • Efficiencies over 90%
  • Annual savings of up to £500 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

Looking to switch to a condensing boiler?