What's the Best Boiler for a Large 5 Bedroom House? Alright, show off...

If you live in a large house, you will likely need an extra powerful boiler. 

For example, if your house has 5 bedrooms, you likely have multiple bathrooms and more radiators than the average home.

These factors mean you have an above-average hot water demand. 

A normal combi boiler won’t usually be suitable in these circumstances, instead, a system or regular boiler will be the best option. 

But how do you know if a combi boiler is right for your home? And which boiler is going to be the best option for a large house? 

Let’s find out...

PS We fit new boilers with gas safe installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.

Is a combi boiler the right type of boiler for your large house?

A combination or combi boiler provides both hot water and heating from a single unit, hence the name.

They provide hot water on-demand, are highly efficient and take their water directly from the mains water supply. 

Combi boilers are the most popular residential boiler installed in the UK and for most small and average-sized homes, they do a great job. However, for large houses, a combi boiler is unlikely to be suitable. 

But, why... why? 

Combi boilers heat cold water on-demand, directly from the mains water supply. They do not store any hot water via a hot water tank so the flow of water can weaken if there is a high demand for hot water. 

This means that if you have multiple bathrooms in your home that are likely to be used simultaneously, a combi boiler may struggle to maintain a strong and consistent supply of hot water to both outlets.

Is a system or regular boiler more appropriate? 

In properties with high hot water demands e.g., one with multiple bathrooms that are going to be used at the same time or with many rooms and therefore many radiators, a combi will struggle and therefore a regular (heat only) or system is more appropriate.

System and regular boilers come accompanied by a hot water storage cylinder that stores large volumes of hot water.

This means that they can provide hot water to multiple outlets simultaneously without any significant change in flow rate e.g., you’ll be able to easily run two or more showers at once. 

There are other rarer circumstances where a combi boiler may not be suitable too, such as in areas with low mains water pressure or a central heating system with old pipework which is particularly sensitive to high pressures. 

You can use our free tool to find out what boilers will be the best for your home, whatever the size.  

Combi, regular or system? 

Got a small or average-sized property? A combi boiler is likely going to be the best choice for you and your home.

If you have a larger property with multiple bathrooms that are likely going to be used at the same time a system or regular boiler is going to be the best choice for you. 

Regular or system? If you already have a regular boiler installed in your home, getting it replaced with a new regular boiler is likely going to be the most appropriate option. 

This is due to the fact that typically regular boilers are installed in properties with old pipework, so may be unable to withstand the high pressures of a more modern system boiler. 

For more in-depth guidance on choosing the right type of boiler for your home, along with the pros and cons of each, check our ultimate guide to the types of boilers. 

For an incredibly basic, and very rough guide:

What size combi boiler do you need for your large house? 

To work out what size combi boiler you need for your house i.e., what the boiler’s power output should be (measured in kW), you can use these general guidelines to get a rough idea: 

• 1 kW for small radiators or towel radiators.

• 1.5 kW for an average-sized radiator.

• 2 kW for a large radiator.

Using the above scores and the number of radiators in your home, add them all together to determine the total kW required.

If you want to read a more in-depth guide on selecting the right size boiler, read our boiler size calculator guide, or alternatively use our boiler tool to get the exact size boiler your home needs. 

What size system or regular boiler do you need for your large house?

Just like combi boilers, system and regular boilers are offered in a range of different sizes (power outputs) starting at 11 kW. 

However, the size of the hot water storage cylinder is another factor to consider.

The majority of storage cylinders are heated via an internal metallic coil.

The coil itself has its own power capacity measured in kW that it requires from the boiler to heat the water in a reasonable length of time, which is referred to as the hot water recovery time.

If you have decided that you think a boiler with a hot water storage tank is the right choice for your home, then you can work out what size system or regular boiler you need, using the following guidelines: 

• 1 kW for small radiators or towel radiators.

• 1. 5 kW for an average-sized radiator.

• 2 kW for a large radiator.

Using the above scores and the number of radiators in your home, add them all together to determine the total kW required. Then add 3 kW to account for your hot water storage cylinder.

Best combi boiler for a large house


As mentioned, if your property is large and you have particularly high hot water demands, a combi is unlikely to be the boiler type for you and your home, at least not your typical combi boiler model.

However, there is one combi boiler model that may do the job...

Introducing the Viessmann 111

The Viessmann 111 is not just a combi or system boiler, it’s a hybrid of the two. 

This is one of the award-winning German brand’s latest innovations, it offers the space-saving and convenience of a combi yet has an integrated storage tank to keep up with the high hot water demands of the modern family home. 

There’s no doubt that the Viessmann 111 is a large boiler, however, if you want to avoid the need to install a separate hot water tank, it’s a suitable compromise.

The Viessmann 111 includes a combi boiler on one side, offering 35 kW of central heating power, and a hot water boiler on the other, offering 35 kW of hot water performance.

So, if you live in a large house and were hoping for the space-saving, on-demand abilities of a combi, yet need it to meet your hot water demands the 111 may be a great choice for you. 

This hybrid model provides you with the ability to run between two to three showers at once, for up to a maximum of 18 litres per minute.

You can read our in-depth Viessmann 111 review if you want to learn more about this powerful boiler. 

Best boilers for your large house 

To determine which are the best boilers available for large homes, we considered the following factors: 

• Warranty period offered by the brand.

• The overall reputation of the brand is based on customer reviews.

• Trustpilot reviews. 

• Awards and accolades e.g. Which? Best Buy Awards.

• Customer service performance.

• The price range of their boilers. 

• Efficiency ratings.

The cost of a boiler doesn’t always necessarily mean it’s better either, so we have included some brands that are considered “budget-friendly” yet are still technically brilliant.

You can read our comprehensive guide in which we rank the best boiler manufacturers, here.

Best system boilers for your large house 

A system boiler comes with a hot water storage tank and so is able to deal with high hot water demands. 

Here are some of the best system boilers available: 

• Alpha E-Tec System Boiler (Low-cost option).

• Viessmann Vitodens 100-W (German engineering).

• Worcester Bosch Greenstar 8000 (Range-topping).

A system boiler is essentially an upgraded version of a regular boiler and with more parts internalised installation is easier.

They also take cold water directly from the mains water supply and so no cistern tank in the loft is required.

This also means there is more flexibility on where the boiler and tank can be installed in the home. 

Got a larger home? You may also be interested in our guide on the best 40kW combi boilers. 

Best regular boilers for your large house 

Regular (heat-only) boilers also come with a hot water storage cylinder and so are also a great option for large houses with high hot water demands. 

Here are some of the best regular boilers available: 

• Alpha E-Tec System Boiler (Low-cost option). 

• Viessmann Vitodens 100-W (German engineering). 

• Worcester Bosch Greenstar 8000 (Range-topping).

Regular boilers are one of the oldest types of boilers available and are still commonly installed in properties with older/traditional heating systems that cannot tolerate the high pressure of the mains.

They are also installed in areas that suffer from low water pressure. 

Best combi boilers for your large house

As previously noted, a combi boiler is not usually advised in large houses with multiple bathrooms and high demand for hot water. 

However, with that caveat, here are some of the best combi boilers that are better able to maintain hefty hot water demands without disruptions to water flow: 

• Worcester Bosch CDi Highflow. 

• Viessmann 111-W (Hybrid).

Best hot water cylinders for large houses 

If you are planning to replace or install a regular or system boiler, you may also need to install a new hot water storage cylinder. 

The type of cylinder required 

For a system boiler, you will need to select an unvented storage cylinder, which takes the water directly from the mains water supply and remains sealed to prevent the water from becoming contaminated. 

If you have a regular boiler, you will need a vented hot water storage cylinder, these are supplied with water from the cistern tank (in the loft). 

What size cylinder is required? 

Like boilers, cylinders also vary in size, as in the capacity of water they can store and it’s essential you choose a tank that matches your home’s hot water demands. 

If you live in a large 5-bedroom house and/or one with multiple bathrooms, you are going to need a cylinder with a capacity of at least 300 litres. Next, you add 40 to 45 litres for each person living in the home. 

However, if you want a more accurate determination of the size of cylinder your house requires, it’s always advised to seek the assistance of a registered Gas Safe Engineer. 

Looking for the best deal on a new boiler? 

If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:

• Gas Safe installation within 24 hours.

• Thousands of satisfied customers with an average score of 4.9 on Trustpilot, surpassing the market leader.

• Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.

• Price match guarantee: We will match any like-for-like cheaper quote.

• Flexible payment options, including interest-free finance.

• Up to 12-year guarantee on selected boilers.

• Fixed price guarantee: No hidden costs.

• Save your quote and decide later.

• Get an instant fixed price on a new boiler, here.

To learn more about boilers, visit our advice section, check out our YouTube channel, or read customer testimonials here.

Heat Happy.