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Which is the Best 24kW Combi Boiler?

Adam Cherry
By: Adam Cherry
Updated: 15th September 2021

Best 24kW Combi Boilers

Small terraced houses, flats or apartments are perfectly suited to a 24kW combi boiler, and these are the best 24kW combi boilers that you should consider:

  1. Ariston Genus One Net
  2. ATAG IC24
  3. Baxi EcoBlue Advance
  4. Ideal Logic Max
  5. Potterton Titanium
  6. Vaillant ecoTEC Pro

Is a 24kW combi suitable for my home?

A combi boiler with a 24 kW output rating is best suited to smaller homes with a single bathroom and around 10 radiators. Larger properties might either be better suited to a combi with a higher output or a different boiler type altogether.

To find the most suitable boiler type and output rating for the heating and hot water demands of your home, you should get the expert opinion of a Gas Safe registered engineer. If the heating and hot water demands of your home requires a more powerful combi, then find out the Best 30kW Combi Boilers with our comparison.

Best 24kW combi boilers

Best 24kW Combi Boilers Seasonal Space Heating Efficiency ErP Rating Warranty
Ariston Genus One Net 90.1% A+* 12 years
ATAG i24C 94% A 10 years
Baxi EcoBlue Advance 89.1% A 10 years
Ideal Logic Max C24 94% A 10 years
Potterton Titanium 92% A 7 years
Vaillant ecoTEC Pro Up to 94% A 2 years

*When used with the Cube RF modulating room sensor that comes with the boiler

Ariston Genus One Net

The Ariston Genus One Net is a highly efficient combi boiler that's available with a lengthy 12 year warranty which will see that you're well covered long after the installation. All Genus One Net boilers come with a Cube RF modulating room sensor which, when used, increases the ErP efficiency rating up to an A+.

  • The very latest soundproof technology ensures quiet operation that's of a similar level to a domestic fridge
  • The unit boasts a large LCD display that's user-friendly and will give you greater control over the boiler
  • A stainless steel heat exchanger that allows for a more efficient transfer of heat and 142% wider waterways greatly reduce the risk of a blockage
  • A 'COMFORT' mode keeps water in the unit warm for instant hot water deliver the next time you turn a hot tap on
  • Modulation of 1:10 ensures that the boiler doesn't use more energy than is needed at that moment in time
  • Lightweight unit (29.7kg) which makes it simple to hang on a wall
  • There's plenty of space within the unit to make servicing, maintenance and any repairs easier for an installer, which could save you money
  • Endorsed by the Energy Saving Trust

As well as this 24 kW model, the Ariston Genus One Net range of combi boilers also includes more powerful outputs of 30 kW and 35 kW.


The ATAG iC range of combi boilers are user-friendly with a number of features that help to increase efficiency to help lower your energy bills. You can even take control of the boiler wherever you are using a smartphone or tablet thanks to being compatible with the ATAG ONE controller.

  • The built-in weather compensator can help to reduce your annual fuel bill by as much as 12%
  • Fitted with an iCon stainless steel heat exchanger that comes with a lifetime replacement guarantee
  • A hot water flow rate of 10.1 litres per minute
  • Runs quietly during operation
  • A flexible flue makes it possible to install the ATAG i24C almost anywhere around the property
  • Available with a 10 year warranty

There are 4 combi boilers in the ATAG iC range with 28 kW, 36 kW and 40 kW models also available.

Baxi EcoBlue Advance

Baxi ecoBlue Advance combi boilers are amongst the most compact units available on the market. Despite their size, Baxi have made sure that these units are capable of delivering central heating and domestic hot water at a powerful rate.

  • Delivers a hot water flow rate of 9.8 litres per minute
  • You could save money on the installation thanks to the unit allowing for front access to all components
  • Installation is also made flexible thanks to a range of flue lengths
  • Endorsed by the Energy Saving Trust
  • Covered by a lengthy 10 year warranty

The 24 kW model is the smallest output in the Baxi EcoBlue Advance range with more powerful 28kW, 33kW and 40 kW units all being available too.

Ideal Logic Max

Ideal are one of the most familiar names when it comes to boiler manufacturers and their trusted range of Logic Max combi boilers are the perfect compact unit for smaller homes.

  • Frost protection to keep the system running through even the coldest of winters
  • A low lift weight makes installation much simpler, potentially reducing costs
  • A hard-wearing and scratch resistant casing
  • The lengthy 10 year warranty can be extended to 12 years when installed by an Ideal Accredited Installer

Ideal Logic Max combi boilers are also available in outputs of 30 kW and 35 kW too.

Potterton Titanium

Likely to be the most budget-friendly of the best 24 kW combi boilers, the Potterton Titanium is still well proven in terms of efficiency and reliability. It's even covered by a lengthy 7 year warranty.

  • Designed to fit within most standard kitchen cupboards
  • Hot water flow rate of 11 litres per minute
  • Get greater flexibility with the installation thanks to 20 metre long flue options
  • Endorsed by the Energy Saving Trust

For properties that have a higher demand for heating and hot water then 28 kW, 33 kW and 40 kW models are also available in the Potterton Titanium range.

Vaillant ecoTEC Pro

Vaillant boilers are well-known for delivering efficiency and reliability in a user-friendly manner and the ecoTEC Pro is no exception. The standard 2 year warranty is one of the shortest when looking at the warranties attached to the best 24 kW combi boilers, but it can be extended to 7 years when the installation is registered with Vaillant Advance.

  • A fully-modulating low NOx burner and fan to increase efficiency
  • Built-in frost protection which helps to ensure that the heating system continues to work during freezing temperatures
  • The 'aquaCOMFORT' mode speeds up the delivery of domestic hot water
  • A modulation range of 1:4 which limits energy usage to increase efficiency
  • Quiet Mark accredited

Plus if you're interested in a renewable heating system then the ecoTEC Pro is fully compatible with the aroTHERM air-to-water heat pump hybrid system.

Vaillant ecoTEC Pro combi boilers are also available in output ratings of 28 kW and 30 kW.

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How much do 24kW combi boilers cost?

Typically, a combi boiler will cost between £500 and £1,500 depending on the model and manufacturer. The potential cost of most of the best 24kW combi boilers fall within that price range with the Ariston and ATAG models being the most expensive.

Best 24kW Combi Boilers Potential Cost (before installation)
Ariston Genus One Net £1,600
ATAG i24C £1,650
Baxi EcoBlue Advance £1,000
Ideal Logic Max C24 £950
Potterton Titanium £775
Vaillant ecoTEC Pro £1,110

These potential costs don't include the installation which you will also need to factor into your thinking when having a new boiler installed. Combi boiler installation costs often fall between £500 and £1,000 but can stretch out to £1,800 depending on the complexity of the installation and rates charged by the installer.

To get the most competitive price for installation, we highly recommend comparing quotes from multiple heating engineers. If you were to only get a single quote then you won't know if you're getting a good deal. Using Boiler Guide, you can get free quotes from as many as 3 heating engineers based in your local area.

Best combi boilers for off-grid homes

For properties that aren't connected to the gas network, finding a new combi boiler isn't quite so straightforward. Without a direct supply of natural gas to fuel the boiler an alternative fuel, such as LPG or oil is needed. Fortunately, some of the best 24kW combi boilers are compatible with LPG.

Best 24kW Combi Boilers LPG Compatible?
Ariston Genus One Net Yes
ATAG i24C Yes
Baxi EcoBlue Advance No
Ideal Logic Max C24 No
Potterton Titanium No
Vaillant ecoTEC Pro Yes

As well as these LPG compatible models, there are also a number of oil boilers that could be suitable for the heating and hot water demands of your home.

Oil Combi Boilers (24kW – 27kW) Output Rating Efficiency Warranty Potential Cost
Grant Vortex Pro 26 kW 94.5% 2 years £2,430
Warmflow Utility UC90HEE 26 kW 89.1% 5 years £1,400
Worcester Greenstar Heatslave II 25 kW 90% 2 years £2,395

How do combi boilers work?

A combi boiler delivers heating and hot water on demand by directly heating water from the mains supply. This means that there's no need for any storage tanks or cylinders, which will free up space compared to having a system or regular boiler installed. However, these will be able to meet higher demand for heating and hot water.

Find out more in How Do Combi Boilers Work?

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We've made finding a local heating engineer easier than ever. Simply complete our straightforward online form, letting us know a few details about the job, and we'll match you with up to 3 heating engineers. Each of these engineers will be in touch to provide their free quote for you to then compare before having your boiler installed at the most competitive price.

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Adam Cherry

About the author

Adam Cherry

Adam is our resident home heating expert. His experience and advice has helped millions of customers improve the efficiency of their homes and save money.

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