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What is a Condensing Boiler?

Go ‘Green’ with a Condensing Gas Boiler

New energy efficient condensing boilers not only save money but reduce CO2

From April 2005 it became law that all new and replacement gas fired boiler installations are to be high efficiency condensing type. The intention is to reduce climate change as these boilers produce less CO2, the upside is you can reduce your heating bill by up to 40% as a result. We take a closer look at the options.

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What is a Condensing Boiler?

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

New condensing boilers can be up to 91% efficient compared to 70-80% efficiency for conventional, non-condensing boilers. This is achieved by 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 91% efficient and that reduces to just 9p 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? blog page.


Types of Condensing Boilers

Condensing is a method that re-uses heat, it’s not actually a type of boiler which enables you, in most cases, to directly replace your old boiler with an equivalent type that also condenses. The most popular types of boiler using the condensing method are as follows…

  • Back Boilers combine a fireplace with the boiler located behind it for central heating and hot water. The only condensing back boiler available is the Baxi Bermuda.
  • Combi Boiler heats hot water on demand and is used widely, not quite as efficient as a regular or system condensing boiler but they can be cheaper to install.
  • Regular Boiler also known as a traditional or conventional boiler and consists of separate controls, cistern and a hot water tank.
  • 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.
Factors to consider Suitable boiler type
Your loft is converted or you wish to convert it. Combi
You have no loft or roof space, 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 have many people in your home & need hot water on demand. Combi
Your current boiler is a back boiler located behind your fireplace Back Boiler

What Next?

In all cases the specification, selection and installation of a correct boiler is a job for an expert, ther are many types and brand of boiler to choose from such as Worcester Bosch, Baxi, Vaillant and Glow-worm amongst others. Correct selection of a boiler is critical so be sure to call in a local reputable plumber from a site such as Boiler Guide or a nationwide firm such as British Gas, they’ll usually visit your home and make an assessment and quote based on your requirements.

* Source: Energy Savings Trust

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