Boilers: How to buy the best boiler Condensing boilers

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Inside a typical condensing boiler

Nowadays, condensing boilers help to drive even better boiler efficiency, making the fuel you're burning to heat your home go further. According to the Energy Saving Trust, replacing an old G-rated boiler with a new high efficiency condensing boiler and improving your heating controls could save you as much as £235 a year.

Here we explain how condensing boilers work and what the key differences are between condensing and non-condensing boiler models.

How condensing boilers work

A high efficiency condensing boiler is a good choice if you're looking for a greener and more efficient boiler, because they're able to make better use of the heat they generate from burning fuels such as gas or oil. 

With a heat only boiler, some heat is wasted in the form of hot gases released from the flue. A condensing boiler captures some of the heat from these gases and uses it to heat water returning from your central heating system. It therefore requires less heat from the burner and is more efficient.

You can find more information on condensing boilers in our boiler review. That has some frequently asked questions on this type of boiler - including condensate pipe freezing.

Condensing boilers vs non-condensing boilers

Both combi and heat only boilers can be either condensing or non-condensing. Building regulations now state that all new boilers installed in a domestic home should be high efficiency condensing boilers, although extremely rare exceptions do apply.

A non-condensing boiler will typically take air in from inside the room, whereas a condensing boiler will be fully sealed and takes air in directly from the outside.

Condensing boilers are safer than non-condensing boilers, as there is a much lower risk of anything being sucked into the boiler. Plus a condensing boiler is typically at least 25% more efficient than a non-condensing model.

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