Understanding combi
and system boilers

Want to talk?

08009128751

Call free

Mon–Sun 7am–9pm

Heating and boilers explained

Very simply, there are two main types of boilers – combination boilers and conventional boilers. If you are unsure what boiler is most appropriate for you and your home, our engineers can talk you through the options at your survey.

  • Combination boilers

    Combination boilers

    Combination boilers have no need for a cold water tank or hot water cylinder which means they are ideal for smaller houses and apartments. They produce hot water on demand meaning that you don't waste money heating up hot water you don't need just to sit in a hot water tank.

    There are some things that you need to consider though in deciding on whether a combination boiler is right for you. We will need to test your mains hot water pressure to ensure you have enough pressure to meet your needs in the home. In addition, there can be a delay of a few seconds while the water heats up.

  • Conventional boilers

    Conventional boilers

    Conventional boilers work by heating hot water and storing in a tank known as a hot water cylinder. You'll often find these in an airing cupboard. One of the big advantages of a conventional boiler is that you can provide hot water to more than one tap or shower at a time. This makes it ideal for larger properties or people who have families using hot water at the same time. Another benefit is that you can fit an electrical immersion heater to the hot water tank giving you backup should there be any issues with your boiler.

    However, there are some considerations with conventional boilers. You need space for it in addition to a cold water tank – such as in an airing cupboard or in your loft. You'll also need controls so that the hot water is heated at the right time for your needs.

    Finally, when using a hot water cylinder, once the water runs out that's it. So if you particularly like lots of baths, its important that you get a right tank for your needs.

New boiler benefits

A new boiler could save you money on your energy bills. However, the savings you make each year will depend on how old and inefficient your existing boiler is. We can help you understand this. Below are some examples on upgrading an old boiler without controls.

Source: Energy Saving Trust

  • Old boiler rating
  • G (< 70%)
  • F (70–74%)
  • E (74–78%)
  • D (78–82%)
  • Semi-detached house
  • £340
  • £255
  • £215
  • £175
  • Detached house
  • £570
  • £430
  • £360
  • £300
  • Detached bungalow
  • £290
  • £215
  • £180
  • £145
  • Mid-terrace house
  • £280
  • £210
  • £175
  • £145
  • Mid-floor flat
  • £145
  • £105
  • £90
  • £70

These are estimated figures based on installing a new A-rated condensing boiler with a programmer, room thermostat and thermostatic radiator controls (TRVs) in a gas-heated home from an older boiler without controls. Savings will vary depending on the size and thermal performance of your home. For more examples, visit the Energy Saving Trust website.

Automobile Association Developments Limited. Registered office: Fanum House, Basing View, Basingstoke RG21 4EA. Registered in England and Wales number 01878835.

More information