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Last updated: 30th September, 2023


Best Combi Boilers for Large Homes (3+ Bedrooms)

Best Combi Boilers for Large Homes (3+ Bedrooms)

Key takeaways

  • Large output combi boilers can service properties with multiple bedrooms and bathrooms more efficiently than smaller kW models.
  • System boilers can be more suited to large properties as a combi alternative, although not as compact, this type of boiler is designed to deal with large water demand.
  • Heat only boilers do not carry some of the benefits that a new combi does, however newer regular (heat only) boilers are still a fantastic option for supplying large houses.

At iHeat, we understand the importance of choosing the right combi boiler to meet the heating demands of larger properties.

We'll focus on renowned brands like Vaillant, Ideal, Alpha, Worcester Bosch, and Viessmann, all offering high-performance boilers known for their efficiency and reliability, they own the lineup for the best combi boilers in the UK. 

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Join us as we delve into the features and benefits of these boilers and help you make an informed decision for your home.

Why a large output is important for larger homes

In larger homes, the demand for hot water is typically larger due to more rooms and water outlets than in smaller houses. 

This is why a boiler with a larger kW output is important, as you can effectively provide both central heating and water without breaking the bank.

Meeting greater heating demand

A larger home, as mentioned, requires an increased heating capacity from its boiler to ensure that every room is adequately heated.

With a larger output combi boiler, you can meet the increased demand for hot water and heat the radiators, providing warm baths, showers, and tap water.

Simultaneous hot water usage

One of the drawbacks of smaller combis is they do not provide sufficient water for multiple bathrooms or simultaneous usage. In contrast, a larger output combi can cope with the demands of numerous showers, etc., being used simultaneously.

This ensures that everyone in the house can take a warm shower whenever needed without coordinating a schedule with other residents.

Comfort and convenience

A large output combi means the central heating system can quickly and efficiently reach the required temperature, providing a comfortable living environment throughout the home.

The need to wait for water to heat up or potentially disruptive temperature fluctuations are negated due to the time saving and convenient duality of the combi.


Future proofing

Getting a larger output combi boiler future proofs your home due to the fact that any expansions or additions to the property can be accommodated for without the need to upgrade your boiler once again.       

Choosing a large output combi can save you the hassle and expense of replacing it later if your needs change.

Other Benefits of a combi boiler:

Water Quality

Water produced from new combi boilers is clean and safe to drink, as it hasn’t been stored in a tank for any amount of time. This reduces the potential of sludge, rust or debris build up contaminating the water supply for a home.


Cheap To Run

Gas is among the most cost effective types of fuel for a heating system, coming in at almost three times cheaper than electricity as an operating fuel.

This indicates once the boiler unit and installation has been paid for, the boiler’s efficiency and low cost fuel will start to pay for itself in money saved much faster than you’d think!



Most modern combis have been designed with operational volume in mind, often excelling in minimising any sound output, with most top of the line boilers being silent when switched on.

Premium boiler brands often receive Quiet Mark awards for their success in acoustical consideration and volume reduction.


Many combi boilers can run on a variety of fuels, gas being the most popular, and can even operate on mains gas or LPG.


Due to their popularity, combi boilers and their replacement parts are very prevalent. This means even if your combi has a problem, their superior availability ensures that there is always an abundance of replacement components that are cheap and easy to source.

Vaillant Combi Boilers 

Vaillant is a trusted name in the heating industry, known for their cutting-edge technology and high-quality products. They offer a range of large output combi boilers suitable for bigger properties. 

The Vaillant ecoTEC Plus and ecoTEC Exclusive models are particularly popular choices, offering outputs of up to 38kW. These boilers combine energy efficiency, reliability, and ease of use, ensuring optimal performance and comfort in larger homes.


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Ideal Combi Boilers

Ideal boilers are renowned for their exceptional performance and value for money. For larger properties, the Ideal Logic Max range offers combi boilers with outputs ranging from 30kW to 40kW. 

These boilers are known for their compact design, energy efficiency, and advanced features. The Logic Max models provide high flow rates, allowing for simultaneous hot water usage in multiple bathrooms and taps, making them ideal for larger households.


Alpha Combi Boilers

Alpha Heating Innovation is a brand known for its focus on innovation and energy efficiency. Their range of large output combi boilers offers excellent performance for larger homes.

The Alpha E-Tec Plus and Intec2 models feature outputs up to 38kW and deliver exceptional heating and hot water capabilities. With advanced controls and modulating technology, Alpha boilers ensure efficient operation while meeting the demands of larger properties.


Worcester Bosch Combi Boilers

Worcester Bosch is a renowned brand recognized for its high-quality and reliable boilers. Their range includes combi boilers suitable for larger households. 

The Worcester Bosch Greenstar CDi Classic and Greenstar Highflow CDi models provide outputs up to 42kW, ensuring ample heating and hot water supply for bigger properties. 

These boilers incorporate advanced features, such as modulating pumps and intelligent controls, maximising energy efficiency and comfort.


Viessmann Combi Boilers

Viessmann, known for their commitment to efficiency and sustainability, offers large output combi boilers designed to meet the demands of larger homes. 

The Viessmann Vitodens range includes models like the Vitodens 100-W and Vitodens 111-W, with outputs up to 35kW and 35.3kW respectively. 

These boilers utilise advanced condensing technology, delivering high levels of efficiency and optimal performance. With their compact design and intelligent controls, Viessmann combi boilers provide a seamless heating and hot water solution for larger properties.


System Boiler Alternative

System boilers perform best in homes with a high hot water demand, specifically either larger properties with a higher number of residents or properties with two or more bathrooms.

System boilers store hot water in a separate cylinder which provides constant flow access but requires additional (minimal) storage space.

System boilers can service multiple flow outlets at one time, meaning no one in a larger home would be standing around waiting for a shower.

What Size (kW) System Boiler Do I Need?

When we talk about boiler size, we’re often referring to the output in kilowatts (kW) as opposed to the physical dimensions of the boiler itself.

Generally the bigger the home the bigger kW combi boiler you will need. Check out the table below to find out which size system boiler is best for your home!




Suitable Size



Up to 10

12-15 kW



Up to 15

18-24 kW



Up to 20


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Heat Only

A heat only boiler provides the heat for a home's central heating system and hot water cylinder. A heat only boiler is suited to servicing larger properties with multiple bathrooms/radiators or a business premises with a high water demand. 

Heat only boilers do require sufficient installation space within a property, as they use two storage tanks (feed & expansion) as well as the aforementioned hot water cylinder. 

Although a combi is generally considered more space saving, a modern heat only boiler is still compact and can supply more bathrooms with hot running water than a combi can.

New boiler costs

As with any boiler type, the unit cost and installation rate for a new combi will be manufacturer and merchant dependent.

iHeat Average boiler installation costs: (updated Sept 2023)

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


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New boiler install


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Back boiler to a combi


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Some location factors that can influence the price of your new boiler

You will be given a specific quote from the boiler installation company based on:

  • Your postcode and specific location

  • The type of home you have (i.e. terraced, semi-detached, etc.)

  • How many bedrooms you have

  • How many bathrooms you have

Choosing the best large output combi boiler is essential for effectively heating larger homes. At iHeat, we recommend considering reputable brands like Vaillant, Ideal, Alpha, Worcester Bosch, and Viessmann. 

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Frequently Asked Questions

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.