What is a Condensing Boiler?

The term ‘condensing boiler’ refers to the fact that the boilers produce condensation from time to time.

Condensing boilers use heat from exhaust gases that would normally be released into the atmosphere through the flue. To use this latent heat, the water vapour from the exhaust gas is turned into liquid condensate.

In order to make the most of the latent heat within the condensate, condensing boilers use a larger heat exchanger, or sometimes a secondary heat exchanger.

Due to this process, a condensing boiler is able to extract more heat from the fuel it uses than a standard efficiency boiler. It also means that less heat is lost through the flue gases.

In other words, 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.

See the Which? website for more information on Condensing Boilers.

Condensing boiler regulations Building regulations that have come into force since 1st April 2005 state that any replacement or new gas or oil boiler must be a condensing boiler. Rare exceptions may apply.