If you're replacing your boiler, one of the first decisions is which type to choose. In most Dublin homes it comes down to a combi boiler or a system boiler. Both are efficient condensing boilers – the difference is how they give you hot water.

How a combi boiler works

A combi (combination) boiler heats water directly from the mains, as you need it. There's no hot water cylinder and no tanks in the attic. Turn on a hot tap and the boiler fires up straight away.

Pros:

  • Hot water on demand – you never run out
  • Frees up space – no hot press cylinder or attic tanks
  • Usually cheaper to install and simpler to maintain
  • Good water pressure at taps and showers, as long as your mains pressure is good

Cons:

  • Struggles if two or more showers are running at the same time
  • Hot water flow depends on your mains water pressure
  • If the boiler breaks down, you have no hot water at all

How a system boiler works

A system boiler heats water and stores it in a hot water cylinder, usually in the hot press. Most of the system's parts are built into the boiler, so you don't need the cold water tanks in the attic that an old-style regular boiler uses.

Pros:

  • Several taps and showers can run at the same time
  • Better suited to larger homes with two or more bathrooms
  • The cylinder can often take an immersion as a backup
  • Works well with solar water heating

Cons:

  • Needs space for the cylinder
  • Hot water can run out if the cylinder is too small, and takes time to heat back up
  • Usually costs more to install

Which is right for you?

  • Apartments and smaller houses with one bathroom: a combi is usually the best fit
  • Family homes with two or more bathrooms: a system boiler is often the better choice, especially if showers are used at the same time
  • Low mains water pressure: a system boiler, sometimes with an unvented cylinder, may perform better

Switching from an old regular boiler to a combi is a popular upgrade, but it means removing the cylinder and attic tanks, which adds to the cost. Our new boiler cost guide covers typical prices.

Get honest advice

The right boiler depends on your home and how you use hot water. Our engineers will look at your home and recommend what genuinely suits it – not just the most expensive option. See our new boiler installations or call 0872 855 624 for a free quote.