Best Boiler for a 4-Bedroom House (UK)

The best boiler for a 4 bedroom house is sized between 18kW and 40kW.

For regular and system boilers, a smaller sized boiler can be sufficient. But for combi boilers, a larger size is needed to provide both heating and hot water from one central unit.

Looking to buy a new boiler for a larger property? The WhatPrice team has put together the following guide to help you choose the best boiler for a 4 bed house.

Introduction

Choosing a new boiler is never a universal decision. If your property has four bedrooms, it will have different heating and hot water demands than a smaller home.

Even then, the age of your property and other factors such as the number of people living in your home will impact which boiler would make the best purchase decision.

Why choosing the right boiler matters

Buying a boiler isn’t something you should do on a whim. That’s because not only are boilers expensive to purchase, but your choice of boiler will also impact your energy bills, plus your overall experience of living in your property.

If a boiler isn’t powerful enough, then you will struggle to heat your home adequately. Likewise, if the boiler isn’t made by a reputable brand, it may experience frequent breakdowns and could even require replacing far sooner than is ideal.

Choosing a boiler that’s too powerful will hike up your energy bills and could even be incompatible with your central heating system. In fact, oversizing the boiler is a common mistake many homeowners make.

Using the information in this guide, we’re here to ensure you purchase the most suitable boiler for your 4 bed property.

Key factors to consider for a 4 bedroom home

What we already know about four bedroom properties is that the heating and hot water demands will be greater than a small flat, or even a typical three bedroom home.

Beyond the number of bedrooms, your plumbing and heating engineer will also be looking at the following to choose the best boiler for a 4 bedroom home:

Age and insulation of the property

When was your property built?	Pre 1900	1920s-1930s	1950s-1980s	1900s	2000s onwards
Insulation levels	Poor	Some insulation	Moderate insulation	Good insulation	Very well insulated

It’s a simple fact that older properties that also haven’t benefited from significant energy efficiency improvements will be more difficult and expensive to heat. Old and inefficient four bedroom properties will need a more powerful boiler to achieve thermal comfort throughout the property.

Examples of energy-efficient measures include: 

• Cavity wall insulation
• Solid wall insulation
• Loft insulation
• Roof insulation
• Floor insulation
• Insulated plasterboard
• Natural material insulation (i.e. sheep wool or hemp)
• New double or triple glazed windows 
• Draught-proofing

Four bedroom homes built after 1990 should boast moderate to excellent energy efficiency as standard. In this case, you won’t have to purchase a larger boiler size (kW) to compensate for poor thermal efficiency.

Hot water demand

Larger homes usually also mean more demand for hot water, especially if multiple hot taps, showers or baths will be in use at the same time.

Combi boilers heat water on demand rather than storing hot water in a tank. While this is fine for smaller homes with one bathroom, combi boilers aren’t designed for homes with more than one bathroom.

Therefore, system or regular boilers are better for busier households.

Existing boiler type

Buying a new boiler is a good opportunity to decide whether your existing boiler type is the right fit for your property.

Granted, you’ll likely be considering a new boiler due to your existing one reaching the end of its lifespan. If upgrading to a more efficient boiler would solve the issue, that’s great.

However, if your boiler type isn’t compatible with your larger property, or you want to switch to a different fuel source, these are all things to think about before you go ahead.

What size boiler do you need for a 4 bedroom house?

Bedrooms	Bathrooms	Boiler type	Recommended boiler size (kW)
4	1	Combi	28kW-34kW
4	1-2	System	18kW-26kW
4	2+	System	27kW-40kW
4	1-2	Regular	18kW-26kW
4	2+	Regular	27kW-40kW

Four bedroom properties require a boiler that’s sized between 18kW and 40kW.

There’s a large size fluctuation here, and that’s because it depends on your boiler type, plus your overall usage needs.

System or regular boilers will only factor in the heat requirements on the property.

In contrast, combi boilers must provide both heating and hot water, which results in needing a larger size boiler.

Factors That Affect Boiler Size (Hot Water Demand, Radiators, Insulation)

Not all 4 bedroom properties are created equal. Instead, the age of your property, its energy efficiency and the number of radiators will determine the boiler size (kW) required.

In general, new build properties or those which are well insulated need less power from the boiler to heat the home. However, older properties will require a bigger size boiler to compensate for heat loss.

The typical four bedroom house has 12-20 radiators. As a general guide, each radiator will require between 1.5kW and 2kW.

Best boiler types for a 4 bedroom house

If your property has four bedrooms, you can choose between combi, system and regular boilers in most cases.

As for which boiler type is best for your home setup, you should consider the following aspects.

Feature	Combi boiler	System boiler	Regular boiler
Heating and hot water supply	On demand (one hot water supply at a time).	Additional tank to be able to supply more than one hot tap at once.	Additional tank to be able to supply more than one hot tap at once.
Cold water tank needed?	No	No	Yes
Hot water cylinder needed?	No	Yes	Yes
Average boiler type energy efficiency (newly installed)	94%	92%	90%
Ideal for more than one bathroom?	No	Yes	Yes
Installation complexity	Easy	Moderate	Complex
Running costs	Lowest	Moderate	More expensive due to heat loss from tank. Running costs can be lower if property is insulated.
Backup hot water?	No	Yes	Yes
Best for	Properties with one bathroom and moderate hot water needs.	Four bedroom properties with two or more bathrooms.	Older properties with four bedrooms. Also, where converting to a system or combi boiler isn’t feasible.

Combi boiler

Since around 80% of UK households have a gas combi boiler, it is technology that most of us are familiar with. Combi boilers provide heating and hot water from one unit, meaning they normally need to be a larger size than other boiler types. Though, they are only recommended for four bedroom homes in limited scenarios, since combi boilers are better suited to smaller properties with one bathroom.

Pros: Combi boilers are extremely energy efficient and easy to install. If extending your home from a three to four bedroom property, a combi boiler might still work for you, especially if your property only has one bathroom.

Cons: Since combi boilers produce hot water on demand, they struggle to provide hot water to more than one hot tap at once. As a result, they aren’t recommended for larger homes with two or more bathrooms, or properties with lots of radiators.

System boiler

Pros: Provides more capacity than a combi boiler, meaning you can use multiple hot taps or showers at once without experiencing a drop in water pressure. New system boilers are almost as efficient as combi boilers.

Cons: System boilers take up more space as they require a hot water cylinder. You must ensure the cylinder meets your hot water demands, or face a wait for the hot water tank to replenish. There are also more components to install and maintain compared with a combi boiler.

Regular boiler

Pros: Regular boilers are the traditional choice for older properties. They can also be fitted with an immersion heater to provide a backup water supply. The storage tanks also allow for a consistent water flow even during periods of high demand.

Cons: These conventional systems take up lots of room and are expensive to install. The water stored in the hot water cylinder can also lose heat which reduces the overall system efficiency.
Top boilers for a 4 bedroom house

To help you choose the best boiler for a 4 bed house, we’ve researched the top rated boiler brands for gas combi, system and regular boilers.

Specifically, boilers which are suitable for properties with four bedrooms based on the manufacturer’s recommendations.

Best Combi Boilers for a 4 Bedroom House

Boiler make & model	Boiler size (kW)	Warranty	Typical cost (excluding installation)
Viessmann Vitodens	025-W 24kW	5 years	£700
Worcester Bosch Greenstar 4000	25kW	10 years	£1,200
Vaillant ecoTEC Plus	26kW	10 years	£1,270
Worcester Bosch Greenstar CDi Compact	28kW	10 years	£1,300
Worcester Bosch Greenstar 8000+	32kW	10 years	£1,600

So long as your four bedroom home only has one bathroom, you can still have a combi boiler. While a system boiler may still be preferable, upgrading to a new combi boiler will be cheaper than converting to a new boiler type.

If you are sticking with a combi boiler, there are some fantastic powerhouses to choose from that are capable of supplying heating and hot water to larger homes.

A great choice is the Worcester Bosch Greenstar range. The Worcester Bosch
Greenstar 4000 25kW has a prestigious ‘Which? Best Buy’ award and boasts a 94% efficiency rating. This boiler is also hydrogen-ready which can help future-proof your central heating system.

Or, if you’re in search of a budget combi boiler, Viessmann Vitodens offers the same size boiler as the Greenstar 4000 25kW but at almost half the cost. While the warranty of this boiler is shorter, it’s an option to consider if you plan to upgrade to something such as a heat pump in the coming years, but aren’t ready just yet.

The Vaillant ecoTEC Plus 26kW is another fantastic option. It features something called
IoniDETECT technology which involves intelligent gas combustion monitoring for improved energy efficiency.

Best system boilers for a 4 bedroom house

Boiler make & model	Boiler size (kW)	Warranty	Typical cost (excluding installation)
Ideal Logic	24kW	5 years	£1,400
Worcester Bosch Greenstar 30i Compact	30kW	10 years	£1,650
Worcester Bosch Greenstar 4000 24kw System	24kW	10 years	£1,450
Vaillant ecoFIT Pure 625 System	25kW	10 years	£1,700
Vaillant ecoFIT Pure 630 System	30kW	10 years	£1,900

For system boilers, we looked at boilers suitable for four bedroom homes that have 16 radiators. With the typical four bed property having between 12-20 radiators, 16 offers a sweet spot.

However, if your four bedroom property has fewer than 16 radiators, you can probably size your boiler down closer to the 18kW minimum size as mentioned at the beginning of this post.

On the cheaper end of the scale, the Ideal Logic 24kW system boiler comes in at £1,400. Ideal advises this boiler is suitable for one bathroom homes, with two bathrooms requiring an upgrade to the 30kW model boiler within this range.

Our other system boilers used the same example specification (a four bedroom home with 16 radiators) but with two bathrooms. This is so we could compare more powerful system boilers designed for larger properties.

Worcester Bosch Greenstar 30i Compact is a lightweight boiler that can fit in a standard kitchen cupboard. It also offers the advantage of being compatible with solar panels, which is ideal if you’re looking to reduce the running costs of your four bedroom property.

Otherwise, Vaillant’s EcoFit Pure range offers plenty of choice. Available as a combi, system or heat-only boiler, this 30kW system boiler is also available in a smaller 12kW model.

Best regular boilers for a 4 bedroom house

Boiler make & model	Boiler size (kW)	Warranty	Typical cost (excluding installation)
Alpha E-Tec 20R Regular Boiler	20kW	7 years	£800
Worcester Bosch Greenstar 30Ri Compact	30kW	10 years	£1,450
Vaillant ecoFIT Pure 425 Standard	25kW	10 years	£1,400
Worcester Bosch Greenstar 24Ri	24kW	10 years	£1,300
Vaillant ecoFIT Pure 435 Standard	35kw	10 years	£2,100

For our regular boilers (also known as heat-only or conventional boilers), we looked at boilers suitable for a four bedroom home and 16 radiators. This provided a suggested boiler size of between 20kW and 35kW.

On the lower end of the scale, the Alpha E-Tec 20R 20kW is a budget-friendly option costing just £800. This boiler is available in 3 sizes (15kW, 20kW and 25kW), making it best for efficient four bedroom properties.

Regular boilers often don’t require the larger sizes as seen with combi boilers. But if a large regular boiler is needed, Worcester Bosch and Vaillant have got you covered.

The Vaillant ecoFIT Pure 435 35kW regular boiler can supply up to 20 radiators and two bathrooms. It’s also compatible with solar technology, and you’ll benefit from Vaillant’s vast network of UK-based engineers if you have any issues.

How to choose the right boiler for your home

Purchasing the best boiler for a 4 bed house relies on tailoring your search to larger properties.

Since the combi boiler market is designed for homes with up to 3 bedrooms and 1 bathroom, you should instead look for boiler brands and models which can meet increased demand.

Beyond selecting a more appropriate boiler for a four bedroom home, there are some additional considerations which can impact both the installation costs and the lifetime costs of your boiler.

Efficiency & running costs

As a homeowner, you’ll be well aware that the cost of heating a 4 bedroom house doesn’t come cheap, especially if the property isn’t energy efficient. The good news is that upgrading your boiler can make a dramatic difference to your energy bills. That said, it’s essential to choose the most suitable boiler type and size for your property to avoid paying for a boiler that is too powerful for what you actually need.

Installation considerations

The cost of installing a boiler will impact the total price. There are various aspects which can either reduce or increase the cost of a boiler installation in a larger property.

Converting your existing boiler type

If you currently have a combi boiler, then you might want to change to a system boiler so that your central heating system is better equipped to handle your demands as a 4 bed home. Converting a boiler may prove to be a smart move, though it will ultimately make the installation more expensive than a like-for-like boiler swap.

Any plans to renovate?

If your property already has 4 bedrooms, the chances of wanting to extend your home to add extra bedrooms are probably slim. That said, if you do plan to renovate your home in the future, and adding more bedrooms or bathrooms is on the cards, ensure your boiler choice is compatible.

Future-proofing your boiler fuel

The government is on a mission to ban boilers powered by fossil fuels such as gas or oil. While both of these boiler types are still readily available, opting for a hydrogen-ready boiler, or another green fuel type can future-proof your home.

Brand reliability & warranty options

At the time of writing, the top 5 boiler brands in the UK are widely considered to include Worcester Bosch, Vaillant, Alpha, Viessmann and Ideal.

Opting for one of the premium boiler brands might mean a higher upfront cost. Although, you’ll usually benefit from better build quality (i.e. stainless steel heat exchangers or smart technology included). Plus, the best boiler brands often have accredited training centres in the UK, which is certainly true of Vaillant and Worcester Bosch.

Be sure to review the boiler warranty carefully. Some manufacturers only offer less than 5 years on the warranty, which is far shorter than the 10-12 years given by others.

There are also certain installation conditions your boiler will need to meet to be able to access longer warranty periods or warranty extensions.

Conclusion & next steps

In summary, the best boiler for a 4 bed house is a system boiler sized between 18kW and 40kW.

Or, if converting to a system boiler is not within budget, remaining with a regular boiler is the next best choice.

Once you inform your plumber of your property specifics (property age, number of bathrooms and the radiator count), you can narrow the boiler size down to a smaller kW range.

Do your research before choosing an engineer to install your boiler. For gas boilers, the engineer must be Gas Safe Registered as a minimum. However, choosing someone who has excellent customer reviews and is also more experienced is recommended.

Need a new boiler? Use our free boiler calculator to get free boiler quotes.

Best boiler for a 4 bed house FAQs

Looking for more advice on buying a new boiler for a 4 bedroom property? We’ve answered some of the top queries below.

For anything else, check out our free boiler content guides where we cover typical boiler costs, plus the best boiler brands to choose from.