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Heating Systems

Replacing your boiler

Boilers account for around 60% of what you spend in a year on energy bills, so an efficient boiler makes a big difference. 

Replacing an old gas boiler with an A-rated high-efficiency condensing boiler and improving your heating controls will significantly cut your home's carbon dioxide emissions - and could save you as much as £300 a year.

How much could you save?

This will depend on how old and inefficient your existing boiler is.

Old boiler rating Annual saving Carbon dioxide saving per year
G ( < 70%) £300 1,220kg
F (70-74%) £200 810kg
E (74-78%) £150 610kg
D (78-82%) £105 420kg

These are estimated figures based on installing a new A-rated condensing boiler and full set of heating controls in a gas-heated, semi-detached home with three bedrooms.

The costs for replacing a boiler will vary, but a straightforward gas boiler replacement will typically cost around £2,300.

Why are new boilers more efficient?

Modern boilers are more efficient for several reasons, but their main advantage is that they are all condensing boilers. All well-maintained boilers burn their fuel very efficiently, but they inevitably lose some heat in the hot gases that escape up the flue. A condensing boiler has a bigger heat exchanger, so it recovers more heat, sends cooler gases up the flue and is more efficient.

Sometimes the flue gases get so cool that the water vapour in the gas condenses out (hence the name). When this happens, even more energy is recovered from the condensing vapour, and the efficiency gets higher still.