What is a Combi Boiler?

A Combination “Combi” boiler combines water heating and central heating systems into one unit.  These systems work independently of each other to heat your home and provide hot water on demand, removing the need for a water tank.  

Combi boilers are generally fuelled using domestic gas supplies, but can utilize LPG or oil if mains gas is not available.

So, is a Combi Boiler right for you?  Here’s a list of pros and cons to help you decide:

  • Combi boilers are extremely energy efficient.  Most have an energy efficiency rating of over 90% – A+ energy ratings.
  • As there is no need for a separate water tank, they are generally a cheaper option if fitting a brand new system – the price of a tank is removed and less new pipework is needed.  The cost of the boiler itself is also generally very competitive in comparison to alternative types of boiler.
  • With hot water available on demand there’s no wait for the water to heat up – no more cold showers!
  • The water is delivered at mains pressure, removing the need for an additional pump to give a power shower effect.
  • The compact size of a combi boiler enables installation in small spaces and the lack of a water tank can provide additional storage space if a tank is being removed.
  • Being a fairly new technology, replacement parts are easier to find and cheaper to buy.


  • You can experience a drop in water pressure if more than once appliance is running that requires hot water.
  • There’s no back up immersion heater if the boiler breaks down – so no hot water or heating until it’s repaired.
  • Cost efficiencies are best with single bathroom houses – for homes with more than one bathroom the economies are less.  The water pressure drop from multiple bathrooms being used might also be an issue.
  • If you are replacing an old conventional boiler with a combi, the old heating system may not be able to cope with the mains pressure.  If the mains pressure is higher than the old system can take then it’s possible that old pipes and radiators would need replacing, adding to the installation cost.

We provide free, no obligation quotations on Combi boiler installation and easy to afford service and maintenance plans.  Click on the button below to find out more.

ODM Heat Care

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Want to know more?

Need help deciding if a Combi boiler is the right choice for your property?  Get in touch and we will provide a free survey of your home and make a recommendation based on our findings.

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