Boiler Replacement

Conventional Boiler vs Combi Boiler [Differences + Costs]

When installing a new boiler into your home, it’s important to choose the correct model to suit your needs.

If you’re choosing between a combi boiler and a conventional boiler, knowing the pros and cons of each, will ensure you make an informed decision.

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What is a conventional boiler?

Conventional boilers, also called ‘traditional’, open vented or regular boilers are connected to the heating and hot water systems that run through a home. This type of boiler is very common in older properties, as they are installed in line with the design and structure of the home.

This system works by having two storage tanks that are usually in the loft – one with a supply of cold water and one that stores hot water.

The cold water tank allows some water to be heated, and then stored in the hot water tank ready to be used when needed. The hot water tank will also supply the central heating system when heating the home.

What are the benefits of a conventional boiler?

  • If there are lots of people in your home, this regular boiler stores enough hot water to supply multiple uses, without the pressure and temperature being affected.
  • If your boiler breaks down, there is still a store of hot water ready to use.
  • They are a better option if you live in a low water pressure area.
  • Better for older buildings that already have a water supply system installed, as they are generally compatible and will be less costly to install.

Combi boiler

Combi boiler is short for combination boiler and are more compact than a conventional boiler.

This means this type of boiler has a combination of a water heater and a central heating system all in one unit, and both household functions are supplied via this boiler.

A combi boiler heats water instantly via the mains, so there is no need for water storage tanks.


  • You don’t need a water storage tank in your home, saving space.
  • As the water is heated instantly, you use less water which is better for the environment.
  • Good water pressure.
  • Better for properties that do not have a loft space.
  • There is less pipework in your home, so less expensive to repair.
  • They are more energy efficient.
  • They are more suitable for modern and new-build homes.
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What are the differences between conventional boilers and combi boilers?

Take a look at the table below to find out the main differences between the boilers, to help you decide which one will work best for you.

  • Conventional boilers are best if your home has a high demand for hot water.
  • Installation of a combi boiler is cheaper as there are less pipes and no storage tanks.
  • If a combi boiler breaks down, there is no water or heating, but a conventional boiler can still provide hot water.
  • Combi boilers provide hot water instantly, whereas conventional boilers take time to heat up water.
  • Combi boilers require less storage space as they don’t need any tanks.
  • Combi boilers are more energy efficient than conventional boilers in a mid-size / smaller home.
  • With a combi boiler, you cannot run more than one bath/shower at a time.
  • A conventional boiler will allow you to have a more powerful shower, as it works using the pressure of the mains.

Combi boiler versus conventional boiler

Is a combi boiler or a conventional boiler the best option for your home? Ask a boiler installer for advice and get your free boiler quotes today.

What are the differences in costs of a combi boiler and conventional boiler?

The costs are an important part if you purchase a boiler with installation.

Below you find the differences in costs between a regular heat only and combination boiler. These costs are based on a ‘same location swap’.

Conventional heat only boiler: A regular heat only boiler costs on average between £1,300 to £2,000 (this includes the boiler, labour costs and VAT).

Combi boiler: A combi boiler installation costs on average between £1,500 to £2,000 (this includes labour costs, VAT and the combi boiler itself).

All new boilers, are condensing boilers

Both new conventional and combi boilers are condensing boilers. Condensing boilers are designed to minimise the heat that is lost up the flue of older non-condensing boiler models, making them much safer and more efficient.

They have a system installed that cools the gases down before they escape, and the condensation that forms during this process is how the boilers got their name

Regulations state that all new boilers fitted in the UK after 1st April 2005 must be condensing models.

This type of boiler is more energy efficient and means you spend less money heating your home, and will also reduce the amount of greenhouse gases that are released into the atmosphere.

Conclusion: Choose a combi boiler if you have a small or mid-size home

If you are looking to replace your current heating system and have a combi boiler installed, it’s key that you are aware of the advantages of the system.

If you have a small home, with only a few occupants, a combi boiler is a great choice because:

  • Combi boilers cost less to install.
  • They provide hot water instantly.
  • They are energy efficient and economical.
  • They are more convenient and simple to install.
  • You will save money on your household bills.

Do you live in a small or mid-size home? A combi boiler may be the best option for you. Request quotes from local boiler installers today.

When is a conventional boiler or system boiler the best choice?

If you have an older or property, your home may be better suited to a conventional or system boiler. A system boiler works in a similar way to a conventional boiler, but they take their water supply from the mains, rather than the storage unit. Your boiler installer may recommend a conventional boiler if:

  • You have a large home with 3 or more occupants.
  • Your family make use of multiple bathrooms at the same time.
  • You have a period property.
  • You have a high demand for hot water.

Is a conventional or system boiler the best option for your property? Ask boiler installers for advice and get your free boiler quotes now.

Get quotes from boiler installers

Not all boilers are suitable for all homes, so it’s essential to check with your local boiler installer before you make a decision.

Obtain free quotes from different boiler installers now.