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Complete Combi Boiler Installation Guide

Everything you need to know about having a combi boiler installed in your home. In this handy guide we answer the most common questions around a new combi boiler installation, including what is a combi boiler?, how do they work?, how much do they cost? & what your best option is.

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Price Guarantee[28]

Simply answer a few multiple choice questions about your existing boiler and we’ll give you a fixed price for a new boiler including all parts and installation[28]

What is a combi boiler?

A combi or combination boiler controls your whole central heating system directly from one, compact unit. Combi boilers are the most popular type of boiler in the UK with more and more people switching from a conventional or traditional system.

Combi boilers are a great option for most homes as they come in a range of sizes and outputs. With this type of boiler you can save much more space than you would with a regular boiler as there is no need for an external water cylinder or water tank. A great advantage of combi boilers is that they give you instant and unlimited access to hot water, as you don’t have to wait for a water cylinder to heat.

Combi boilers are also an energy efficient option as all modern combi boilers are condensing so they use much more of the energy they produce and less is wasted. Condensing boilers make more use of the energy supplied by extracting heat from flue gasses that would have otherwise been lost by a non-condensing boiler. Combi boilers are usually quicker and cheaper to install, since there’s no requirement for a water cylinder meaning less pipe work is needed.

How do combi boilers work?

Combi boilers work by having one compact system heating both your hot water and radiators so there is no need to have an additional external cold-water tank or hot water cylinder. Combi boilers provide instant hot water, by constantly being on standby when there is no water demand. As soon as you turn the hot water tap, the boiler will kick in and the water will become hot very quickly. When the request for hot water is trigged by someone turning on the hot tap, this signals the boiler to start heating water inside of the system. The heat exchanger transfers the majority of the heat from the burnt gas inside the boiler to the cold water, and then delivers it to the taps as required.

Inside combi boilers, the control valves operate in different directions to either allow water to flow through the central heating system or divert it to the appropriate hot water tap as required — but never both at the same time. You can pre-set your desired temperature and the boiler will work with the room thermostat to ensure your home is heated as you like.

How much does a combi boiler installation cost?

The price of a combi boiler can depend on several things, such as the size of your home and the complexity of the boiler installation.

When someone needs a new boiler, one of the first questions they have is ‘How much will a new boiler cost?’. In the UK, most people replacing their boiler are likely to choose a combi boiler as they are great for saving space in your home.

The cost of the combi boiler itself will be much lower than the overall price given by an installer, usually because they’ve also included the cost of installation on top. Whilst the cost of installation may seem expensive, it's important to note that a new boiler should always be installed by a Gas Safe registered engineer who will follow strict protocol checks and procedures. Having an experienced Gas Safe registered installer ensures peace of mind that the installation has been completed to the highest regulated standards.

There can be a substantial difference in boiler prices so if you want to know how much a combi boiler costs it’s best to get an online quote for your home. This will take into account your current central heating system, the boiler fuel type and how many radiators you have to give you an accurate price.

Our prices for a new combi boiler, with installation included are great value and we have a range of boiler brands and fuel types available. The price of a new combi boiler can depend on the brand you choose to have installed but it’s important to remember that you shouldn’t compromise on quality. If the price of a new boiler is particularly low, it’s worth checking to make sure the boiler itself is manufactured to a high standard to avoid additional repair costs at a later date.

We only install high quality boilers from reputable brands so you have the peace of mind that you're getting the best for your budget. Our boilers come with a manufacturer backed warranty of up to 10 years[5] so you can be assured of how long lasting they are.

What is the best combi boiler for me?

There is a wide choice of combi boilers available with a range of brands available. Recommending the right boiler will largely depend on your home and needs. If you have a lower demand for hot water or a smaller home then a boiler with a lower output might be most suitable. The higher your hot water demands are, the higher the output of boiler you will need. As a general guide you can learn what the best combi boiler is for you by considering what your needs are based on size, price and performance.


The size of your home will have a huge impact when determining what the best combi boiler is for you. Combi boilers are a great choice for a wide range of homes in the UK as they are powerful enough to deliver large amounts of instant hot water. However, if you have a very large home with a high demand for hot water then a combi boiler may not be a suitable option.


The price of a combi boiler is a major influential factor when deciding which boiler is best suited. It's important to make sure that a new boiler installation is always performed by a Gas Safe registered engineer. If the price you are being quoted seems too good to be true, it could be that the engineer is not well qualified which could have huge consequences. To keep price down, you could consider installing the new boiler in the same place as the existing one and avoid purchasing additional features that are not required.


Different boilers have different performance levels based the home they are heating. If you have a small home, the best combi boiler may be one with a lower output. Because the house is smaller, the demands on the boiler for heating and hot water will be less. In the same way if you have a larger home, you may require a boiler with a larger output as it will need to deliver a more powerful performance in order to supply the demand required.

If you're not sure what the best combi boiler is for you then let us help you to choose. With nearly 20 years of boiler installation experience you can trust us to recommend the right boiler for you, our simple online quote tool will provide you with the best option boiler for your home.

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[5] Subject to an annual service at the customer’s expense. Warranty extension from 5-years to 7-years or 10-years only available on Worcester Bosch. Warranty extension from 5-years to 10-years available on Ideal Boilers. All warranty extensions subject to an additional charge.

[28] Exclusions apply. See