What are the different types of domestic boilers and which is best for you?

Every new domestic boiler that’s installed in the UK has to be a condensing one ie one which uses a heat exchanger to re-use heat which would usually escape into the atmosphere. This increases energy efficiency, lowers heating bills and reduces carbon footprint.

There are three main types of condensing gas boilers: combi boilers, system boilers and conventional (also called traditional, regular, open vent or heat-only) boilers.

Combi Boilers








Combi boilers are probably the most cost-effective residential boiler for most homes. They control both hot water and central heating, and their energy efficiency makes them the unit of choice for environmentally-conscious homeowners. Heating water directly from the mains and whenever a tap is turned on, you can get unlimited hot water whenever you need it. There’s no need for a cylinder or water tank, saving you space in your home and cutting down the installation time.

They’re one of the UK’s most popular choices when it comes to home heating because they have plenty of advantages for homeowners:

  • No waiting time for hot water and central heating
  • Compact choice for homes with less space
  • Water delivered directly from the mains
  • Provide powerful showers without the need for a pump
  • Easier to maintain since there’s generally less pipework to be installed
  • Much lower risk of pipework freezing
  • No need for loft space

However, a combi boiler may not be the best choice for all homes and there are some drawbacks:

  • May not be the best choice for homes with low water pressure
  • Not possible to run two baths or showers at the same time
  • Leaks can cause loss of water pressure
  • Not ideal for larger homes

System Boilers








If your home has more than one bathroom, a system boiler could be the perfect option. They require a hot water storage cylinder, but not a water tank, and because many of the main components are actually built into the system, your boiler installation will be relatively quick and painless. Both the pump and the expansion vessel are inbuilt, eliminating the need for header tanks. As there’s no need for a tank, a system boiler frees homeowners from worrying about frost damage or leaks, while it also makes them much easier to maintain. For larger homes with multiple bathrooms, particularly if there’s no space for a tank, system boilers are a great choice.

Their benefits include:

  • Economical running costs
  • Compact and space-saving design
  • Constant supply of hot water
  • No need for an expansion cistern
  • Compatible with solar thermal systems, making them a very energy-efficient option

Unfortunately, they do have some disadvantages:

  • May have to wait for hot water to reheat if it runs out
  • Need to find space for the cylinder
  • Size of your tank dictates how much water you can use
  • Requires insulation in order to stop heat loss

Conventional Boilers 








Conventional boilers, also known as traditional, regular, open vent or heat only boilers, are comprised of both a cylinder and a water storage tank. Although they’re not the best option if space is at a premium, a conventional boiler is able to supply large volumes of hot water to multiple bathrooms, making them a great choice for larger households. It’s probably best to remember that this sort of unit is best suited to homes which already have traditional heating systems in place. Your pipework may not need changing at all, but if it does, any changes are likely to be minimal. Like system boilers, they can be used in conjunction with solar heating systems, helping you to reduce your energy bills and ecological footprint.

Advantages include:

  • Can supply water to multiple bathrooms and taps at the same time
  • Ideal for homes in areas with low water pressure
  • Compatible with solar thermal systems, making them a very energy-efficient option

While some of the downsides are as follows:

  • Not a compact option
  • Hot water isn’t available on demand and may need time to warm up
  • Installation can be more expensive and complicated due to the need to install both a cylinder and a tank

What Type of Boiler Do You Need?

If you are looking for a replacement boiler, it’s best to keep in mind that every home has different heating requirements, and that every different boiler system has a range of unique properties as described above.

In general, tank-based home boilers (system and conventional) are best for properties with multiple bathrooms, while combi boilers are the most appropriate choice for smaller homes/flats with just one bathroom and perhaps a shower room.

Which makes do I recommend?

There are many domestic heating brands and makes in the marketplace but if I had to make a recommendation I’d always plump for two brands;

Worcester Bosch and Ideal. Why? I like them for the following reasons:

  • build quality is very good so reliability tends to be excellent
  • they are both manufactured in the UK
  • warranties are very good
  • after sales care is good
  • parts and spares are readily available
  • out of all the sytems on offer I find these makes relatively easier to repair and to service which keeps my costs down.

I hope you find all this information helpful. If you’d like me to quote for a replacement system just get in touch via this enquiry form.





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