Condensing boilers are the most efficient type of home heating system. They work by recovering wasted heat from conventional boilers and using it to carry on heating up the water. In conventional boilers, the gases created in the heating process escape through a flue and into the atmosphere. A condenser uses these hot gases to pre-heat the incoming water, which reduces the amount of work the boiler has to do. A condensing boiler will normally pay for itself in bill reductions in under three years.
All new gas central heating boilers fitted in the UK since 2005 have to be condensing boilers, except in exceptional circumstances. It is possible to fit a condensing boiler to an existing, non-condensing system, but it will probably require locating the boiler elsewhere.
