What is a Back Boiler?

Back Boilers (also known as back boiler units or BBUs) became popular in 1966 with the launch of the original Baxi Bermuda.


A back boiler is a small, compact boiler fitted at the back of an open fireplace hearth. It sits behind a gas fire and provides hot water and central heating to the property.


Back boilers were popular until the Building Regulations changed in 2005, when it became a requirement to install high efficiency condensing boilers. Although many have been replaced with wall-hung condensing boilers, there are still a large number of back boilers still installed in UK homes.


An old standard efficiency back boiler is less than 70% efficient – so for every £1 of gas burned, on 70p worth of useable heat is generated and the other 30p worth is lost up the chimney. By replacing it with a new boiler at over 90% efficient, fuel bills can be reduced by up to £305, according to the Energy Saving Trust.

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Related FAQs

How does a system boiler work?

A system boiler has all the main components of the heating system within it, allowing a neat and quick installation. The boiler heats water stored in a cylinder or tank, delivering hot water when required and is particularly beneficial in properties that have a high demand for hot water.

Where is safe to install a boiler?

You can have your boiler installed safely in most rooms. However, you do need to consider the Building Regulations.

What is a condensing boiler and how does it work?

A condensing boiler is a boiler that recaptures and reuses the heat from combustion gases that would normally be lost through the flue. There are three main types of condensing boiler: combi, system, and heat only boilers

What temperature should my boiler be set at?

Typically, your boiler should be set to at least 65 degrees Celsius to prevent bacteria growing in the water and maintaining comfort.

What is the Boiler Upgrade Scheme?

The Boiler Upgrade Scheme (BUS) provides eligible homeowners a grant of up to £7 500 to help with the cost of low-carbon heating systems such as air source heat pumps.

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