Most homes have a central heating system with radiators. The system is typically fuelled by mains gas, oil or LPG. The job of the boiler is simply to heat water which is then piped round the building to heat radiators or provide hot water for washing and bathing.

The Energy Saving Trust estimates that boilers account for around 55% of what you spend in a year on energy bills, so an efficient boiler makes a big difference.

Whilst most modern, well-maintained boilers burn their fuel very efficiently, condensing boilers are also able to recover more heat from the hot gases that older, non-condensing boilers emit from the flue, thus increasing its efficiency.

If you were to replace an old gas boiler with an A-rated high-efficiency condensing boiler, and improve your heating controls, you could save around £310 a year on your fuel bill as well as reducing your home’s carbon emissions (source: Energy Saving Trust: based on replacing ‘G’ rated gas boiler in a semi detached 3 bed house). The cost of new boilers varies considerably but typically comes in around £2,300 to replace.

Some houses rely on electrically fed storage heaters, generally using lower priced Economy 7 electricity. The heat is then released through the day. This is an expensive way of heating your house and one common complaint is that there is not enough heat left in the radiators during the evening when it is needed.

What do I need to consider when choosing a system?

There are a number of factors to consider if it is time to change your boiler:

1. What type of fuel type should I go for?
Gas: If you have mains gas, then a gas boiler is usually the cheapest heating system option available to you.
Oil or LPG: If you are not connected to the gas grid it is likely that you use an oil or LPG boiler. It might be that you live near a mains gas pipe in which case you can look at having the property connected (WREN could help you with this).  If there is no gas pipe near your home then this is not an option. It is still worth considering installing an efficient condensing oil or LPG boiler though.
Biomass boilers: If you are not on the gas main, you may also consider a wood-fuelled or biomass boiler. These burn logs, pellets or wood chips, and are connected to your central heating and hot water system. These boilers do cost quite a lot to install (between £7000 and £20,000), but their fuel is less expensive than oil or LPG, and they also attract funding via the Renewable Heat Incentive (£1000 to £6000 per year for 7 years). See our section on Biomass Boilers. 
Heat Pumps: Heat pumps may be an option for you if you live in a well-insulated modern building, preferably with underfloor heating, and do not have a mains gas connection.

2. What type of system should I chose?

There are three main types of boiler:

  • conventional boiler (also known as regular or vented boiler),
  • system boiler (also known as a sealed system) and
  • combi boiler (combination boilers):

Conventional boiler – this system comes with a hot water storage cylinder and an expansion tank which is generally located in the loft.  The system is often fed by a cold water storage tank (also usually located in the loft). The system is ideal for houses with greater hot water requirements, i.e. larger families, and can complement PV/Solar Heating systems.
System boiler - like a conventional system, this works by storing hot water in a cylinder; however they do not require a feeder or expansion tank in the loft. The system is also ideal for houses with greater hot water requirements, i.e. larger families, and can complement PV/ Solar Heating systems
Combi (combination boiler) – this system does not store hot water in a tank or cylinder but rather heats water directly from the mains supply on demand. This restricts the amount of hot water you can draw from the system at any one time. This system is ideal for houses with less demand or where space is limited.

NB. All of the above systems can use condensing boilers.

Once you have decided on the type of boiler, you then need to make sure that you choose the most efficient model and ensure that the installer matches the boiler output to your heating requirement.