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Last updated: 30 January 2024

Best Small Combi Boilers For Home Heating In The UK 2024


Are you on the lookout for a compact boiler for an apartment or smaller home? Luckily, boiler size does not have to come at the expense of performance and output. Several impressive small combi boilers on the market can comfortably meet your heating needs and still fit in a kitchen cabinet.

Combi boilers are as efficient as boilers get, so even if they may sometimes be more expensive than the cost of a system boiler, they are very likely to be cheaper to run in the long run depending on your consumption. 

In this article, we’ll be breaking down the best compact combi boilers of 2024 in the UK, as well as their specs, prices, and performances. From across the board of manufacturers, we’ve compiled the top 5 best small combi boiler ranges, here’s a first look:

Small combi boiler rangeDimensions (HxWxD)Key benefit
Intergas Compact ECO RF590 x 450 x 240Innovative built-in feature that allows heating engineers to remotely track your boiler performance.
Glow-worm Compact626 x 400 x 270Exceptionally quiet operating volume, making it an ideal choice for smaller spaces.
Bosch Greenstar CDi Compact690 x 380 x 280The smallest and most efficient boiler ever manufactured by Worcester Bosch, renowned for its compactness.
Bosch Greenstar Si Compact690 x 390 x 280Highly efficient boiler with an ErP rating of A (up to 94%) that can still comfortably fit in a kitchen cupboard.
Ideal Logic+ Combi Boiler700 x 395 x 278Extensive 10-year warranty that covers both parts and labor, helping save costs on monthly maintenance contracts.

Got your eye on a small combi boiler already? Save yourself hours of endless research and vetting by letting us handle it for you. Here at Household Quotes, we can ensure you get the best deal for your money by providing you with 3 free, non-binding quotes from trusted installers right in your area. Simply fill out our 30-second form and sit back while we handle the rest. 

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Differences between compact and small combi boilers

You may have noticed that the terms compact and small are not always used interchangeably when talking about combi boilers. That’s because each term can refer to a slightly different boiler aspect. 

When talking about small boilers, it usually refers to the actual heat and power output the boiler is capable of. A boiler with a small output is more suited for homes with smaller heating needs. This can be seen in the number of radiators and/or bathrooms in your home.

When talking about compact boilers, it usually refers to the dimensions of the boiler unit itself. Luckily, there are plenty of combi boilers with impressive performance that can still be tucked away in a cupboard. 

The cost of a combi boiler can differ based on its size and output, but also depending on the boiler manufacturer and their popularity.

The best small combi boilers 

To make sure that you choose the best compact combi boiler for your home, we’ve taken the liberty of collecting key specifications about each boiler for a comprehensive overview. Here are some of the specifications we’ll be discussing, and what they mean:

  • Output DHW: Standing for Domestic Hot Water, this indicates how powerful the boiler is, and its capacity for meeting your hot water needs.
  • Output CH: Since combi boilers provide both hot water and home heating, they have two output ratings of which the latter is central heating. This indicates the capacity of your boiler to meet your home heating needs. If your home lacks a central heating system but you would like one, it is best to check out central heating prices to form the best price estimate for your home.
  • Efficiency: The ErP directive is an EU-initiated rating system that indicates the amount of generated energy an appliance can efficiently use, instead of it being lost. In this case, if your boiler is 90% efficient, that means only 10% of the energy is lost. The highest efficiency for compact combi boilers is an A-rated boiler with up to 94% efficiency. This means that for every £1 spent on heating, only 6p is wasted. The cheapest heating will likely be provided by A-rated boilers due to this efficiency.
  • Warranty: A warranty will indicate the period in which boiler repairs, malfunctions, and new parts can be covered by the manufacturer. Ideally, you’d want this to be as long as possible to ensure that unwanted costs don’t build up.
  • Price: When considering all the specifications for each boiler, the cost of a new boiler can help you decide which boiler gives you what you need for the fairest price. Remember that premium boilers will tend to have higher prices simply based on their material quality and product reliability.
  • Lift weight: Compact boilers are designed to be space-saving and discreet and can be mounted vertically onto a wall or inside a cabinet. For this reason, boiler lift weight lets you know its capacity to be mounted safely on a vertical surface.

Intergas Compact ECO RF

  • Dimensions (HxWxD): 590mm x 450mm x 240 mm
  • Output DHW: 22kW, 28kW, 32kW
  • Output CH: 18kW, 23kW, 27kW
  • Efficiency: A-Rate / 93%
  • Warranty: 10 years
  • Price: £990 – £1,155
  • Lift weight: 30kg, 33kg, 36kg

Founded in 1939, Intergas is a Dutch company with a stellar reputation for innovation and efficiency. Although it may not ring a bell as quickly as Worcester Bosch or Ideal, Intergas is nothing short of a pioneer in boiler technology. In 1996, Intergas introduced the first biothermal heat exchanger, something that is today a standard component in pretty much all boilers. 

The Intergas Compact Eco RF range includes some of the smallest boilers on the market, the smallest being the Eco RF 24. With a heating output of 18kW, it’s ideal for smaller homes with just 1 bathroom, and up to 10 radiators. 

The Eco RF 30 and Eco RF 36 are slightly larger, but still very much compact. Each has a respective heating output of 23kW and 27kW, making them adequate for heating slightly larger homes with 1 bathroom, and up to 15 radiators. 

Perhaps most impressive, all models in the Intergas Compact Eco RF range come with an extensive 10-year warranty, demonstrating the confidence of the manufacturer in their product quality and performance. 

Glow-worm Compact

  • Dimensions (HxWxD): 626mm x 400mm x  270mm
  • Output DHW: 24kW, 28kW
  • Output CH: 18.3kW
  • Efficiency: 92%- 93%, ErP A
  • Warranty: 5 years 
  • Price: £540 – £650
  • Lift weight: 25kg, 26kg

Glow-worm is a UK-based boiler manufacturer with almost a century of experience in the field. Now a part of Vaillant, another well-established and respected manufacturer in the UK, Glow-worm continues to impress with its quality and efficient energy solutions. 

Their range of small and lightweight Compact combi boilers are ideal for homes seeking space-saving, yet powerful heating. With an output range of 24kW – 28kW, Glow-worm Compact boilers can comfortably meet the needs of small to medium-sized homes with up to 15 radiators. 

With the ability to easily mount onto walls, this compact boiler can seamlessly tuck away into a kitchen cabinet and reduce the clutter in your environment. Particularly impressive is the whisper-quiet operating volume of this boiler range, ensuring peace in your home. For homes beyond the reach of the gas grid, the Glow-worm Compact range is also available with LPG fuel compatibility. 

Bosch Greenstar CDi Compact

  • Dimensions (HxWxD): 680mm x 390mm x 280mm
  • Output DHW: 28kW, 32kW, 36kW
  • Output CH: 24kW
  • Efficiency: 94%, ErP A
  • Warranty: 7 years 
  • Price: £1,00 – £1,370
  • Lift weight: 32.9kg

Worcester Bosch’s Greenstar CDi Compact is one impressive boiler range, offering a combination of compactness and sheer power, making it an ideal choice for medium to large-sized homes with 2 bathrooms and up to 20 radiators. 

Despite its compact size, this boiler range delivers some of the highest outputs among our mentioned models, making it a reliable option for more spacious homes. This compact powerhouse of a boiler also comes with built-in smart controls for enhanced convenience, customisation, and control. 

The Greenstar CDi compact range exhibits an impressive hot water flow rate of up to 14.7 liters per minute, able to fill a kitchen sink with scalding hot water in just 37 seconds, according to Bosch’s testing. 

If you’re seeking a boiler that combines efficiency, power, and compactness all in one product, the Worcester Bosch Greenstar CDi Compact is nothing short of a great choice. 

Bosch Greenstar Si Compact

  • Dimensions (HxWxD): 690mm x 390mm x 280mm
  • Output DHW: 25kW, 30kW
  • Output CH: 24kW
  • Efficiency: 94%, A ErP
  • Warranty: 10 years
  • Price: £975 – £1,160
  • Lift weight: 32.9kg

Worcester Bosch truly stands as a beacon of trust and performance in the UK heating industry, having earned its well-founded reputation since 1962. The Greenstar range has even secured a Which? Best Buy Award for seven years in a row, so it is only right to have it on our list. 

The Greenstar Si Compact boiler range is space-efficient and lightweight, comfortably tucked away in a standard kitchen cupboard. The 25Si Compact – with a 25kW heating output – is ideal for smaller homes, while the 30Si Compact can meet the needs of medium-sized homes with a single bathroom.

Worcester Bosch’s extensive user features ensures unparalleled control over your comfort, even letting you use wireless internet-enabled controls to operate your boiler from a distance. Most useful, this range is also compatible with 20% hydrogen blends, making the Greenstar range future-proof. LPG alternatives for homes not connected to the gas grid also exist. 

Worcester Bosch boiler costs vary depending on the boiler model, output, and size, but the Greenstar Si Compact certainly stands out as a great bargain for an even greater boiler.

Ideal Logic+ Combi Boiler

  • Dimensions (HxWxD): 700mm x 395mm x 278mm
  • Output DHW: 24kW, 30kW, 35kW
  • Output CH: 24kW
  • Efficiency: 94%, ErP A
  • Warranty: 7 years
  • Price: £968 – £1,156
  • Lift weight: 36kg

Ideal is renowned for its affordability and extensive warranty packages, with some of its boilers boasting up to 12 years of coverage. The Logic+ range has been celebrated with multiple awards, such as Good Housekeeping’s Reader Recommended Status in 2013 and 2017, and Which? has credited Ideal as a trusted trader for warranty service.

The Logic+ combi boiler range is powerful enough to provide ample heat and hot water for small to medium-sized homes with ease. Additionally, the Logic+ features a unique patented heat exchanger exclusive to Ideal that comes with its own 10-year warranty, a testament to Ideal’s trust in its product quality. 

The Logic+ range is also future-proof due to its compatibility with a 20% hydrogen blend and its ability to run on LPG for homes not connected to a gas grid. 

For those seeking cheaper ideal boiler prices, the Ideal Logic Max is a great option that offers the same compact dimensions and available outputs as the Logic+. The main difference is the additional system filter that helps extend the life of your boiler by preventing waste debris from building up in the system.

Choosing a boiler range is just the beginning of the journey. Regarding installations and potential costs, it is highly recommended to consult a professional Gas-Safe registered heating engineer for the best advice on your home’s unique needs.

Lucky for you, Household Quotes can free you from hours of burdensome research and phone calls to find the perfect installer. By filling in our quick and easy form, we can help you get one step closer to your boiler with 3 free quotes from reliable local installers. No hidden charges or extra obligations. Click below to begin!

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Which is the smallest combi boiler in the UK?

Regarding dimensions, the smallest boiler available in the UK is the Intergas Compact ECO RF 24 model. With a height, width, and depth of 590mm x 450mm x 240 mm respectively, this wall-mounted compact boiler comfortably fits in any standard kitchen cupboard with ease.

Equipped with vacuum insulation technology, the Intergas Compact ECO RF 24 operates with little to no noise, making it a perfectly silent option for smaller homes. 

What is the smallest (kW) combi boiler?

Regarding output, the smallest combi boiler on our list is once more the Intergas Compact ECO RF 24 model. This particular model has a domestic hot water (DHW) output of 22kW and a central heating (CH) output of 18kW respectively. 

This makes the Intergas Compact ECO RF 24 a suitable option for smaller homes that are looking to save on space. It is important to note that this smaller kW output makes this model best suited for homes with 1 bathroom and up to 10 radiators. 

What size small boiler do you need for your household?

Getting a compact boiler for your home does not necessarily have to mean you settle for a mini heating output! Many of the compact boilers mentioned above are very capable and reliable in providing steady heating for your home.

A slim combi boiler comes with a wealth of benefits, most notably being the smaller dimensions that allow your boiler to tuck away in a cupboard and free your home from clutter. Many small combi boilers are also optimised to operate with minimal sound, ensuring a peaceful living environment even in close quarters.

While a combi boiler unit can sometimes be larger than a system or conventional boiler, it will still take up far less space in your home. This is because combi boilers do not require any additional units, such as a hot water cylinder or cold water tank. 

When choosing a compact boiler for your home, it is highly recommended to consult with a licensed professional installer to get the best picture of what your home needs and how much the installation might cost. However, with so many installers on the market, how can you know you’re not overpaying?

Luckily, we’re here to help you out. Through our services at Household Quotes, our friendly experts can ensure that you choose the best quality boiler and installation services for your needs at an optimal price. Simply fill out our 30-second form and receive up to 3 free non-binding quotes from our network of licensed professional installers right in your area. 

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Akif Aliyev
Written by Akif Aliyev, Writer

Akif has a keen interest in green home improvement solutions and the role of digital media in identifying climate trends. He aims to provide a multidisciplinary approach to content rooted in credible research and accuracy.

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