Combi Boilers Guide

A new combi boiler will reduce your energy bills and make your home more energy efficient.

However households with 2 or more bathrooms might want to consider other options as a combi might not be the best option.

Compare combi boiler prices from installers in your area by completing the form at the top of the page.

In This Combi Boiler Guide:

What is a combi boiler?

A combi (or combination) boiler provides heating and hot water on demand, direct from your boiler. They combine both a high efficiency water heater and a central heating boiler, within one compact unit.

Combi boilers save on space in your home as no separate hot water tank is required and they involve less pipe work. They are generally cheaper to install because of this.

A combi boiler delivers hot water through your shower or taps at main pressure, with no need for a pump. They are therefore good for providing you with a powerful shower.

Combination or combi boilers are currently the most popular choice of boiler in UK homes.

How do combi boilers work?

Combi boilers heat water directly from the mains supply, as and when you need it. This means there is no need for water storage tanks or cylinders.

Combi boilers are often more powerful than conventional ones because they need power to heat water instantly to keep up with demand.

The diagram below explains how a combi boiler works in your home:


How much is a combi boiler?

A new combi boiler will typically cost around £1,200 - £3,000. As a general rule, bigger boiler sizes will cost more.

If you are replacing your old boiler for a new boiler, you can reduce the price you pay by seeing if your installer will trade-in your old boiler. Your old combi boiler could be traded in for as much as £400.

To learn more about boiler prices, see our guide to boiler costs.

To get the best price for your combi boiler, you should compare a number of quotes from a mix of national and local boiler installers.

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How much will I save with a combi boiler?

Modern combi boilers are super efficient and can convert at least 90% of fuel into heat. When compared to the millions of old boilers in the UK which convert at around 50%, efficiency savings on a new combi can be as much as £350 a year.

Old boilers with an efficiency of 50% are essentially wasting 50p for every £1 you spend on fuel. If you have an old inefficient boiler you could well be quids in by updating to a new super efficient combi boiler. A 90% combi boiler means that for every £1 spent on fuel, 90p goes towards heat.

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Is a combi boiler right for me?

Combi boilers are perfect for you if you’re looking for a boiler that is:

+ Ideal for a smaller home

+ Ideal for space saving

+ Cost efficient

+ Energy efficient

+ Able to provide a powerful shower

+ Ideal if you only have one bathroom

If you have more than one bathroom, you may want to consider other boiler types (see below).

What alternatives are there to a combi boiler?

Alternatively, you can install either a system boiler or a conventional boiler. The boiler system that works best for your home will depend on both your heating requirements and the size of your home.

For example, system boilers are great for homes with two or more bathrooms, they are economical to run and don’t require a water tank in the loft.

Conventional boilers, however, are ideal if your home has two bathrooms and are a good option if you already have a traditional heating and hot water system.

Click here to find out which boiler is best for your home, or read on to find out more about combi boilers.

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Who manufactures combi boilers?

Combi boilers are manufactured by the following companies, all of which are trusted names within the industry:

Baxi has been manufacturing boilers in the UK for 150 years. They produce mid range boilers, which are fairly reliable and very efficient. All new Baxi boilers are endorsed by the Energy Saving Trust™. In an independent survey by consumer review magazine Which?, Baxi’s Duo-tec combi 28 HE boiler was voted the best overall boiler of 2015. Baxi boilers tend to cost less to buy and install than some other boiler brands, including Worcester Bosch and Vaillant.

Glow-worm is a British brand of boilers, produced by the Vaillant group. This economical boiler range is fairly reliable and budget friendly, with generally low purchasing costs. Glow-worm boilers can also save space, their Flexicom range of combi and conventional boilers are compact enough to fit in a small cupboard.

Ideal Boilers
Ideal is a well-known British brand, which has been manufacturing boilers since 1905. The Ideal range of boilers are fairly reliable and most of their boilers come with a five year parts and labour guarantee. The Ideal range of Logic+ and Logic combi boilers are efficient and small enough to fit in a kitchen cupboard.

Vaillant are one of the market leading boiler brands in the UK and are generally considered to be highly efficient, quality boilers. An independent survey by consumer review magazine Which? (2015) showed Vaillant to be one of the most reliable boiler brands. Vaillant boilers don’t tend to be the cheapest, but could work out as good value for money in the long run. Their ecoTEC boiler range has won awards, including the Which? Best Buy Award, 2012.

Worcester Bosch
Worcestor Bosch are one of the market leading boiler brands in the UK and are generally regarded as high quality, efficient boilers. During an independent survey by consumer review magazine Which? (2015), consumers showed Worcestor Bosch to be one of the most reliable boiler brands. In 2015 Worcestor Bosch updated its Greenstar gas boiler range in line with new energy efficient standards and this range has won the Which? Best Buy award for six years running (2010 - 2015). Worcestor Bosch boilers tend to incur a premium price, but could work out as good value for money in the long run.

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What are the leading combi boilers?

The following table shows which combi boilers are best, based on central heating output and the average price with installation:


Product name

Product number

Max. central heating output (kW)

Average price with installation*

EcoBlue+ 24
Ideal Boilers
Logic plus 24 HE
Worcester Bosch
Greenstar 24i Junior
ecoTEC Pro 28

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What are the pros and cons of combi boilers?


  • Take up less space
  • Allow you to use your loft as a living space (bedroom)
  • Instant access to hot water
  • Can run multiple showers in a row without waiting for water to heat up in between
  • Less pipe and invasive work needed to install them


  • Do not store hot water
  • Struggle to provide hot water for multiple appliances at the same time
  • Not ideal for large houses with multiple bathrooms

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Should I get a combi boiler?

If you live in a small to medium sized house or flat then you will likely be better off with a combi boiler. Not only will it save you much needed space, you will also have access to instant hot water. Combi boilers should be considered in any house which has only one main bathroom, and possibly an en suite.

If you live in a larger house with at least 2 bathrooms you can still consider a combi boiler, but you may need to invest in a powerful one to meet your needs. A conventional boiler may be more beneficial if space is not an issue and you are likely to be running more than one shower or bath at a time.

Speak to a professional today by filling in the form at the top of the page. We will put you in touch with a select few local installers who can offer you free advice and no-obligation quotes, tailored to your home.

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How do I get the best price for a combi boiler?

We recommend getting at least 4 quotes from 3 boiler installers. It’s also worth comparing local installers prices to national companies as local installers can often be more competitive.

You can complete the form at the top of this page to compare prices of up to 4 local and national installers operating in your area - compare prices now.

See also:

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