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Which is the Best Boiler for a 4 Bedroom House?

Adam Cherry
By: Adam Cherry
Updated: 6th October 2021

Best Boiler 4 Bedroom House
Combi or system boiler? That's the question. And the answer comes down to whether your 4 bed house has 1 or more bathrooms.

If you have the 1 bathroom then a combi boiler will get the job done. Any more and we recommend turning to a system boiler. This is because system boilers are built to meet higher demand for hot water by storing it in a cylinder.

We also need to think about how many radiators you have. The boilers we've compared can comfortably heat between 10 and 15 radiators.

4 bedrooms with 1-2 bathrooms (combi)
Baxi EcoBlue Advance 33 vs Worcester Bosch Greenstar 8000 Life 30

4 bedrooms with 2+ bathrooms (system)
Ideal Logic Max System S24 vs Vaillant ecoTec Plus 624

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The difference between combi and system boilers

Combi boilers are all-in-one heating systems. Everything it needs to provide heating and hot water is within the boiler itself. So whether you turn the heating or hot water on, the boiler will set to work straight away to provide them instantly. Thanks to this, they're compact and cost-effective heating systems as you don't have to buy a hot water cylinder too.

With a system boiler, you will have to install a hot water cylinder. And while that does mean it needs more space than a combi, it's not bad news. You see, thanks to storing hot water in a cylinder, a system boiler can meet higher demand for hot water than a combi. So if your home has 2 or more bathrooms then you'll be needing a cylinder.

Not sure which boiler is best for your home? Compare them further in Combi vs System Boilers.

Best combi boiler for a 4 bed with 1 bathroom

It's hard to beat Baxi and Worcester Bosch when it comes to combi boilers. They both offer highly efficient models that are covered by an extensive warranty or guarantee.

Boiler Feature Baxi EcoBlue Advance 33 Worcester Bosch Greenstar 8000 Life 30
Central Heating Output Rating 29.6 kW 30 kW
Domestic Hot Water Output 33 kW 30.2 kW
Seasonal Space Heating Efficiency 93% 94%
ErP Efficiency Rating A Heat, A Water A Heat, A Water
Standard Warranty / Guarantee 10 year warranty 5 year guarantee
Max. Extended Warranty / Guarantee 12 year guarantee
Mounting Wall Wall
Dimensions in mm (HxWxD) 763 x 450 x 342 780 x 440 x 365
Potential Cost £1,405 £1,300
Typical Installation Costs £500 - £1,000 £500 - £1,000


All modern gas boilers are highly efficient because they have to be condensing (by law). This essentially means they turn more fuel into heat for your home than a non-condensing boiler. You want an efficient condensing boiler as this will help to lower your heating bills – and your carbon footprint!

The efficiency of a boiler is measured as a percentage. You can see that these boilers are very closely matched but the Greenstar 8000 just takes it by 94% to 93%. To give you an idea of what this means:

  • You spend £1 heating your home
  • 94p goes towards heating your home
  • 6p worth of heat is carried out of the flue pipe and away from your home by waste gases

When it comes to gas boilers (oil, LPG and biomass too) they can never achieve 100% efficiency. There will always be some waste.

Sizing (output rating)

All boilers have a central heating (CH) output rating. The higher the number – which is measured in kilowatts (kW) – the better suited it will be at heating more radiators.

Combi boilers also have a domestic hot water (DHW) output. This shows the level of demand for hot water from taps, baths and showers it's able to meet.

As these combi boilers are both well suited to homes with 4 bedrooms and 1-2 bathrooms, their output ratings are closely matched. The biggest difference is that the Baxi has a higher DHW output of 33 kW compared to 30.2 kW.

Give What Size Boiler Do I Need? a read to make sure you get output rating right.


Healthy Boiler Warranty
Baxi boilers come with a warranty while Worcester Bosch offer a guarantee. The key difference here is that a warranty is a promise from the manufacturer to inspect any issues. If the fault falls inline with the terms and conditions then they'll fix the boiler. A guarantee is a legal promise that the manufacturer will repair the issue. Again, this must be within the manufacturer's terms and conditions.

As standard, the Baxi EcoBlue has a 10 year warranty. That's double the length of the standard guarantee of 5 years on the Worcester Greenstar 8000. However, choose to have the Greenstar 8000 installed by a Worcester Accredited Installer and this can be extended to 12 years.


As these combi boilers are very similar there isn't much between them in terms of price.

You also need to think about the installation costs. Which, for these boilers will likely be somewhere between £500 and £1,000. To get the most competitive price for the installation of a new boiler, we highly recommend comparing quotes – get free quotes today.

So, which is the best?

Both of these boilers are reliable, efficient and will be able to heat your 4 bed house effectively. There really isn't much to separate them. However, we must crown a winner and that's the Worcester Bosch Greenstar 8000 Life.

If a heating engineer recommends a slightly higher DHW output for your home then the Baxi EcoBlue Advance 33 could do the job.

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More combi boilers to think about

While Baxi and Worcester Bosch both offer great options for a 4 bed house, they're not your only options.

The combi boilers in the table below all have a central heating output between 26 kW and 32 kW. A size well suited to homes with 4 bedrooms and up to 15 radiators.

Combi Boiler CH Output DHW Output Potential Cost
Alpha E-TEC Plus 29.7 kW 32 kW £925
ATAG IC35+ 31.2 kW 40.3 kW
Ideal Vogue Max C32 26 kW 32 kW £1,206
Intergas Xclusive 36 26.6 kW 36.3 kW £1,150
Viessmann Vitodens 100-W 32 32 kW 34.9 kW £1,175

Best system boiler for a 4 bed with 2+ bathrooms

The best system boilers for a 4 bed house will have an output rating of between 18 kW and 26 kW. Homes with more radiators (up to 15) will need an output rating closer to 26 kW.

We've chosen to compare the Ideal Logic Max System S24 and the Vaillant ecoTEC Plus 624. Both of these are great options for a 4 bed house.

Boiler Feature Ideal Logic Max System S24 Vaillant ecoTec Plus 624
Central Heating Output Rating 24.2 kW 24.4 kW
Seasonal Space Heating Efficiency 94% 94%
ErP Efficiency Rating A Heat A Heat
Standard Warranty 10 years 5 years
Max. Extended Warranty 10 years
Mounting Wall Wall
Dimensions in mm (HxWxD) 700 x 395 x 278 720 x 440 x 340
Potential Cost £1,049 £1,227
Typical Installation Costs £500 - £1,000 £500 - £1,000


Modern system boilers can all heat a home very efficiently. This is thanks to condensing boiler technology which simply means they're able to capture more heat than non-condensing boilers.

An efficient boiler will help to lower your heating bills because it doesn't need to use as much fuel as an older boiler. Both of these system boilers are equally matched when it comes to efficiency with ratings of 94%.

Sizing (output rating)

Boiler Size
To meet the heating demands of a 4 bed house with 10-15 radiators, a system boiler needs an output rating of 18 kW to 26 kW. These boilers are at the higher end of that scale so can meet higher heating demands.


Ideal offers a standard warranty twice as long as the ecoTEC Plus (10 years compared to 5 years). However, Vaillant gives you the option to extend the warranty to 10 years when installed by a Vaillant Accredited Installer.


The Vaillant ecoTEC Plus is likely to be the more expensive option – around £1,227 compared to £1,049.

Remember, as you're installing a system boiler then you'll also need a hot water cylinder. Then there's the installation costs on top of this which are likely to be in the region of £500 to £1,000. We recommend comparing quotes to find the best deal.

Best system boiler for a 4 bed house

These system boilers are very evenly matched. There's very little between them in terms of efficiency, output rating and warranty. The biggest difference is price. Vaillant's ecoTEC Plus 624 is potentially the more expensive option at £1,227. The Ideal Logic Max System is still over the £1,000 mark but only slightly at £1,049.

As you could stand to save some money on the boiler itself, we're crowning the Ideal Logic Max as the best system boiler for a 4 bed house.

More system boilers for a 4 bed house

All of the system boilers in the table below also fit the mould of a suitable boiler for a 4 bed house with 10-15 radiators.

System Boiler CH Output Potential Cost
Ariston Clas HE System Evo 24 24 kW £725
ATAG i24S 23.2 kW
Baxi 818 18 kW £889
Intergas Compact HRE SB 18 18.7 kW £785
Viessmann Vitodens 100-W 19 19 kW £995
Worcester Bosch Greenstar 21i System 21.6 kW £1,034

Now you're ready for the next step

Once you've compared boilers and found the right one for your home, it's time to compare installation quotes. Comparing quotes from a few different companies will give you the confidence that you're hiring the right person for the job at the most competitive price.

You can get free quotes for a new boiler from installers right here on Boiler Guide. All you need to do it complete our simple online form and up to 3 installers will soon be in touch. It’s never been easier to get quotes.

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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