Condensing boilers are what we call models of heating boiler which get their name because they enter what is called "condensing mode" periodically. In other words, they start to extract heat from the exhaust gases that would otherwise escape through the flue, in the process turning water vapour from the gas back into liquid water or condensate.

The condensing boiler can come as either oil or gas fired models.

A condensing boiler makes much more efficient use of its fuel than a non-condensing boiler. Its high operating efficiency is made possible by the design of the condensing boiler's larger - or sometimes dual - heat exchanger.

The heat exchanger makes sure that as much heat as possible is transferred from the boiler's burner - and as little as possible lost in gases through the flue. There are two types of condensing boiler: regular and combination. Regular condensing boilers heat your hot water through a hot water cylinder in conjunction to meeting the space heating requirements. Combination condensing boilers give you instant hot water without the need for a cylinder.

Please bear in mind that not all home heating systems will be compatible with a combination boiler. A qualified installer will tell you which type of condensing boiler, regular or combination is most suitable for your home.

Replacing an old boiler with a new A rated condensing boiler and a full set of heating controls can save up to a quarter on your heating bills straight away and up to 1,300kg of CO2 year.