Professional carrying out a combi boiler installation

How Does a Combi Boiler Work? Understand Your Combi Boiler Installation

Combi boilers work by heating water when you need it for your home heating and washing facilities. They’re a great choice for lots of homeowners, as there are plenty of different models to choose from.

Combi boiler installations are different to other boilers because they’re just one compact unit. System boilers and conventional boilers, on the other hand, have a hot water tank, and conventional boilers have a cold water tank too.

Is a combi boiler the best type of boiler for your home? Our guide to the Pros and Cons of a Combi boiler may also but but read more below on how combi boiler installations work to find out.

How does a combi boiler work?

Combination boilers are different to other types of boiler because they heat water on demand. When you put your heating on or turn on a hot tap, your combi boiler will start heating cold water from the mains. System and conventional boilers, on the other hand, warm up water ahead of time and store it in a hot water tank for when you need it.

Because combi boilers work by heating water straight from your water supply, they provide hot water at mains pressure. This is different to system and conventional boilers, which provide hot water at whatever pressure your installation’s working at.

Is it a good idea to install a combi boiler in my home?

Fitting a new combi boiler installation in your home could be a great decision. But it all depends on your property, household and hot water needs – a system or conventional boiler could turn out to be a better choice.

If you’re convinced that a combi boiler’s right for you, complete our quick online form to get free quotes from local boiler installers. Otherwise, take a look at our pros and cons list to help you decide.

Combi boiler pros

Combi boiler cons

Hot water available 24/7

Combi boilers can provide hot water whenever you need it. Combi boilers work almost instantly, so just switch on your heating or turn on a tap whenever you need to.

Unsuitable for large households

The majority of combi boilers aren’t ideally suited for bigger households with a high demand for hot water. If you want to use multiple showers at the same time, even the most powerful combi boiler could struggle.

Economical and efficient

Just pay for the hot water you need with a combi boiler. When system and conventional boilers heat and store water, you can end up spending money heating water you don’t need. But with a combi boiler, you’ll only ever pay for hot water you use.

High pressure not guaranteed

Although combi boilers are capable of providing a strong hot water supply, if your water supply’s not very good, a combi boiler won’t make it any better. Plus, they don’t work with electric power showers, so installing one actually rules out a way of improving it.

Can provide a high pressure

Combi boiler installations heat water directly from your mains supply. This means that if you normally have a good cold water pressure, you’ll have a great hot water one too.


Combi boilers don’t need a hot water cylinder or cold water tank – they come in just one compact unit. This means that a combi boiler installation is a great choice if you have a home with limited space.

Reduced pipework

Because combi boilers have less components, they need less pipework too. This means they’re cheaper and less complicated to install than other types of boiler.

So, a combi boiler could be a great choice for you, but it all depends on your needs. If you want a new boiler without having to change your shower, find out what your options are here.

How to get a quality combi boiler installation

If you’ve come to the conclusion that a combi boiler is the type of boiler installation you want, there are a few more things you need to decide on. These include:

  • How powerful your boiler needs to be
  • What hot water flow rate you require
  • Your preferred boiler manufacturer

How powerful your boiler is is measured in kW – it’s often referred to as its ‘size’. It’s important to get a boiler that’s powerful enough to meet your needs, without paying for more than you need. Your hot water flow rate is similar – this is how much hot water your boiler will produce in one minute and needs to suit you and your property.

There are quite a few boiler manufacturers out there – you might want to buy a specific model made by a certain brand. If you want to know more about different boiler manufacturers, take a look at Which?’s handy article.

When you buy a new gas boiler, it’s important to get it installed by a Gas Safe registered engineer. That way, you’ll know it’s safe, legal and set up properly. A reliable professional will also be able to give you expert advice on the cost of a new boiler, and supply and install a model that suits your budget.

Start finding reliable local professionals today

If you need to get in touch with reputable boiler installers in your area, we can help. Simply:

  • Pick the boiler replacement service you need below
  • Fill in the quick form
  • Select ‘GET FREE QUOTES’ and get matched with local boiler engineer

All the boiler engineers we’ll put you in touch will be on the Gas Safe register, so you don’t need to worry. Start getting your free quotes to begin saving money on your heating now!

Evy Coe

Evy works for Quotatis as a Content Marketing Executive. She loves to write about interior design and help homeowners with their DIY projects.

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