"Heating and hot water accounts for over half of what you spend in a year on energy bills, so an efficient boiler makes a big difference.

All modern, well-maintained boilers burn their fuel efficiently, but they inevitably lose some heat in the hot gases that escape up the flue (a pipe used to extract fumes and supply fresh air to the boiler).

Modern boilers are more efficient than older boilers for several reasons, but their main advantage is that they are ‘condensing’. A condensing boiler recovers more heat from the exhaust flue gas and uses it to heat the central heating water, making it more efficient than older boilers."

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- Energy Savings Trust