Helping UK homeowners save money on their heating

condensing boiler illustration

What is a Condensing Boiler?

The condensing boiler is a far more efficient alternative to non-condensing boilers. They’re able to capture more heat without using any more fuel and release fewer carbon emissions into the atmosphere.

Thanks to being so efficient, all boilers installed in the UK must now be condensing by law.

What is a condensing boiler?

A condensing boiler has a Flue Gas Recovery System. When burning fuel, a boiler produces water vapour which contains heat. Thanks to the Flue Gas Recovery System, a condensing boiler captures this heat and uses it to heat the home. Heat that would otherwise be lost through the flue pipe of a non-condensing boiler.

Simply put, condensing boilers convert more gas (or oil) into useable heat. This results in higher efficiencies, reduced running costs and lower CO2 emissions (greenhouse gasses).

Modern condensing boilers achieve efficiencies of over 90%. Compare that to the 70-80% of non-condensing boilers and it’s instantly clear why all boiler replacements must be condensing. To achieve such efficiencies, condensing boilers have a highly effective heat exchanger within the flue which captures wasted heat and re-uses it.

Typically, condensing boilers are more expensive due to their greater complexity but are capable of reducing central heating bills by up to 40%*, re-couping the extra expense.

Boiler efficiency can be best described in monetary terms. If a boiler is 78% efficient then that’s equivalent to 22p being wasted for every £1 you spend on gas. Compare that to a condensing boiler that is 93% efficient and that reduces to just 7p being wasted – a big difference.

More details about high efficiency condensing boilers and how they can benefit you can be found at our in-depth – What is a High Efficency Condensing Boiler? article.


Condensing boiler regulations

Condensing boiler technology will help to significantly lower the carbon emissions produced from home heating. As a result, all gas and oil boiler installations must be condensing. Condensing boiler regulations state the following:

  • New gas boiler installations and gas boiler replacements must be condensing.
  • New oil boiler isntallations and oil boiler replacements must be condensing.

These regulations were introduced from 1st April 2005 for gas boilers and 1st April 2007 for oil boilers. So, if you’ve had a boiler installed since these dates then it’s a condensing boiler.

Condensing boiler benefits

If you hadn’t guessed already, there are many benefits to heating your home with a condensing boiler.

  • Highly efficient: They’re able to convert more than 90% of the fuel into heat for your heating and hot water
  • Lower your heating bills: Being so efficient means that you could see your heating bills drop – particularly if it’s replacing a non-condensing boiler.
  • Reduce your carbon footprint: Fewer carbon emissions are emitted out into the atmosphere so you’ll be reducing your impact on the planet.
  • Take up less space as they’re more compact: They don’t need the same level of ventilation as non-condensing boilers so they take up less space.
  • Increased safety: As ‘sealed’ heating systems they only take air from outside (non-condensing boilers take in air from within the property).

Types of condensing boilers

Condensing boilers are often confused as being a ‘type’ of boiler. However, all boilers are condensing no matter whether they’re a combi, regular or system boiler – which are all types of boiler. Let’s take a look at each of these boiler types in a little more detail:

  • Combi boiler: Delivers heating and hot water on demand without the need for any additional tanks or cylinders, making them compact and cost-effective heating systems for properties with 1 bathroom.
  • Regular boiler: Also known as traditional, conventional, open-vent and heat-only boilers, these are the oldest boiler type available. As well as the boiler itself, they need to be installed alongside a feed and expansion tank and a hot water cylinder. Due to the extensive pipe network needed to connect these parts, they’re only recommended for properties with a regular boiler already installed.
  • System boiler: Similar to a regular boiler but with an important difference, the boiler contains an expansion vessel which means the feed and expansion tank is not required in the loft, saving space. A hot water cylinder will be needed though and while this will take up more space, it allows them to meet high demands for hot water – great for properties with 2+ bathrooms.

The boiler type best suited to your home will depend on the size of your property, your existing heating system as well as demand for heating and hot water.

Factors to consider Suitable boiler type
Your loft is converted or you wish to convert it Combi or system
You live in a flat or bungalow Combi
You have more than 2 bathrooms System or regular
You experience low mains water pressure System or Regular
You have an old boiler and want to upgrade an existing conventional boiler to high efficiency boiler System, Regular or Combi
You want hot water on demand Combi

How much does a condensing boiler cost?

As all boilers must now be condensing, it’s better to consider the potential cost in terms of boiler type. The total cost of a new boiler (including installation) is likely to fall somewhere between £1,000 and £3,500. This isn’t set in stone though and prices can vary fairly significantly depending on:

  • Boiler manufacturer and model
  • Boiler type (combi, system or regular
  • Complexity of the installation
  • Whether it’s a like-for-like boiler replacement
  • Rates charged by the installer

The table below shows how much you might expect to pay depending on the type of boiler being installed.

Type of Boiler Potential Cost Cost of Installation Total Cost
Gas combi boiler £500 – £2,000 £500 – £1,000 £1,000 – £3,000
Gas system boiler £500 – £2,500 £500 – £1,500 £1,000 – £3,500
Gas regular boiler £500 – £3,000 £500 – £1,500 £1,000 – £3,500

Is it time for you to get a new boiler?

The time to replace a boiler eventually comes to us all. After all, boilers don’t last forever. So, how do you know when the time is right to replace your boiler?

  • It was installed 8 or more years ago – boilers tend to have a lifespan of 10-15 years
  • You’re having to call out a heating engineer to repair your boiler on a regular basis
  • Your existing boiler isn’t condensing (all gas installations from 1 April 2005 will be condensing)
  • You’ve noticed that your heating bills have been on the rise
  • The heating around your home simply isn’t as effective as it used to be

Get free new boiler quotes

If the time has come for you to replace your boiler then you’ll need a fully-qualified heating engineer. This means finding a Gas Safe registered engineer to install a gas boiler and an OFTEC technician for oil boiler installation.

Whichever type of boiler you’re having installed, you can connect with heating engineers in your area using Boiler Guide. Simply take a few moments to complete a simple online form and you’ll get free no-obligation quotes from up to 3 installers.

Why 3 installers? Well, comparing multiple quotes is an important part of finding the right heating engineer for the job. This is your opportunity to compare customer reviews, experience and, of course, price. Once you get a quote that you’re happy with, you can go ahead with the condensing boiler installation confident you’ve hired the right company for the job.

* Source: Energy Savings Trust

Post navigation


You may not realise it, but your boiler accounts for 55-60% of your annual spend on...

Post navigation


Important notice about this article: Please note that the Feed-in Tariff (FiT)...

British Gas Boiler Offer

0% APR for 3 Years on a New Boiler from British Gas

FREE Boiler Quotes

Get 3 FREE boiler quotes from local trustworthy heating engineers now

Warmzilla New Boiler Offer

Get a fixed price quote on your new boiler now!


British Gas Boiler Offer