size of boiler
Last updated on: 29 August 2024

24|7 Home Rescue – What size of boiler do I need?

When choosing a new boiler, there are many important decisions you’ll need to make. From the boiler type to the brand and model, you’ll need to ensure that the system you select is a suitable fit for your home and needs.

Amongst the most important factors when selecting a new boiler is the size of the system. Your boiler’s size will determine its ability to cope with your heating and hot water demands, so it is essential that you make the right choice.

In this guide, we’ll provide you with everything you need to know about boiler size, including a boiler sizing rule of thumb to help you understand the kind of boilers that would be best suited to your property and your needs.

How is boiler size measured?

How is boiler size measured?

The size of a boiler is measured in kW output. This measurement indicates how well a boiler can cope with your heating and hot water demands. You can measure the boiler size required for your property by considering the number of radiators and bathrooms within your home, as well as the number of rooms. It is often suggested that you add together kW of all radiators for boiler size suggestions.

Typically, the larger the size of the home, the higher the heating and hot water demands – thus the larger size of boiler needed. Likewise, a smaller home can be supplied with sufficient central heating from a smaller boiler size.

Why is boiler size important?

Why is boiler size important?

The size of a boiler is important as it will have an impact on the system’s ability to meet your heating and hot water needs – it can also significantly affect your energy bills. If you choose a boiler too small, it will struggle to meet your heating demands and this can result in frequent boiler breakdowns and faults. Not only can this be highly inconveniencing, but it can also be expensive as repair costs can be high; especially if you don’t have sufficient boiler cover.

Contrastingly, if you select a boiler system that is too large in size, this can lead to excessive energy use and high energy bills. Considering the current rise in energy rates, an overactive boiler is the last thing anyone needs.

Thus, it is significantly important that you choose a boiler that has a suitable kW output for your home and needs. Not only will this help to ensure that your needs are effectively and efficiently met, but it can also help you save and provide you with peace of mind in knowing that the system you have installed is right for you.

Try our free online quote tool today to find out the size of boiler needed for your home.

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What size should my boiler be?

What size should my boiler be?

When deciding which boiler size is most suitable for your home, there are a number of factors that you’ll need to consider. Firstly, you’ll need to consider the boiler type best suited to your home.

There are three types of boilers used within the UK, namely: combi boilers, heat only boilers and system boilers. The sizing for each of these boiler types works differently.

Below, we provide a brief outline of each boiler type and issue a boiler sizing rule of thumb for each system. For more information on the different types of boilers, visit our boiler type guide.

Combi boilers

A combi boiler is a type of boiler that is renowned for its compact size and energy efficiency. These systems are designed to provide both hot water and heating without any additional tanks or cylinders.

Combi boiler sizing

Combi boilers are typically best suited to small to medium households. These smaller properties are usually a 24kw boiler size of house. Although some brands, such as Worcester Bosch, manufacture powerful combi boilers in sizes of up to 50kW, you should still bear in mind that combi boilers have restrictions on their hot water supply. Combi boilers cannot deliver hot water and heating simultaneously, so they may not be suitable for households that have a high demand for hot water.

To help you get a better understanding of combi boiler sizing, we’ve provided the following table as a combi boiler sizing rule of thumb. The below figure details different boiler sizes and the types of properties they are typically best suited to:

Boiler SizeNumber of bedroomsNumber of radiatorsNumber of bathrooms
24kW – 27kW1-2Up to 101
28kW – 34kW2-3Up to 151-2
35kW – 42kW4+Up to 202+

 

To get a personalised recommendation for a combi boiler size for your property, try our free online quote tool today.

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Heat-Only Boilers

Heat-only boilers are designed to provide heating and hot water using an additional cold water tank and a hot water cylinder for storage. These systems are the traditional form of heating in the UK, and they can deliver hot water to multiple taps at once.

Heat-only boiler sizing

Heat-only boilers are a great choice for larger properties, for example 30kW – 40kW is the typical size of boiler for a 4 bed house. For significantly large homes with high hot water and heating demands, some boiler brands manufacture heat-only boilers in sizes of up to 50kW.

Here’s a heat-only boiler sizing rule of thumb to help you decide which size heat-only boiler is best suited to your home.

Boiler SizeNumber of bedroomsNumber of radiatorsNumber of bathrooms
12kW – 15kW1-3Up to 101
18kW – 24kW2-3Up to 151-2
30kW – 40kW4+Up to 202+

 

Why not try our free online quote tool today to get a bespoke recommendation for a suitable boiler size for your home and needs?

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Get your new boiler and save your heating bill yearly with new energy efficient boiler.

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System boilers

System boilers, like heat-only boilers, are a common choice for larger homes with high hot water and heating demands. These systems provide both hot water and heating through the use of an additional hot water cylinder for storage. Unlike heat only boilers, system boilers do not require a cold water tank as most of their heating components are already built into the system.

System boiler sizing

System boilers are an excellent choice for larger homes due to their ability to deliver hot water to multiple taps at once. For example, a 30kW – 40kW system boiler could be recommended as the typical size of boiler for a 4 bed house.

A system boiler could also be a suitable option for you if you want to save space in your property, as they do not require an extra cold water tank.

Here’s a system boiler sizing rule of thumb to provide you with a better insight into system boiler sizes.

Boiler SizeNumber of bedroomsNumber of radiatorsNumber of bathrooms
12kW – 15kW1-3Up to 101
18kW – 24kW2-3Up to 151-2
30kW – 40kW4+Up to 202+

Finding the right boiler size with 247 Home Rescue

Finding the right boiler size

At 247 Home Rescue, we know how important it is for you to get the right boiler for your home and needs installed. We’re a team of home heating specialists with a wealth of knowledge and expertise in all types of boiler systems, from combi boilers to heat-only and system boilers. Our team are on hand to help you make the best choice for your home heating, whether you’re in need of recommendations for the size of boiler for a 4 bed house or a 2 bed property.

Why not try our free online quote tool today? This is the best way to get an idea of the size of boiler required for your home. Simply answer a few easy questions about your home and heating needs, and in just a few seconds, you’ll be provided with a free quote detailing the ideal boiler size for your property, along with a bespoke estimate for the cost of your new boiler installation. We also offer a number of boiler finance options to help you spread the cost of your new boiler over an agreed timeframe. Get in touch with us today to find out more about our flexible payment plans.

Try our free online quote tool today for a personalised recommendation of a boiler best suited to your needs, along with a bespoke quote for your new boiler installation. Alternatively, contact us on 0333 242 2524 to speak to one of our expert advisors.

FAQs

How to Calculate Size of Boiler Required?

The best way to calculate the size of boiler required for your home is to count the number of radiators that are used within your household. The more radiators around your home, the larger your boiler system will need to be. You should also factor in the number of bathrooms that are within the property, as this will provide an idea of how low or high the hot water demand is in your household.

To get an insight into the size of boiler needed for your property, you can refer to our boiler sizing rule of thumb tables above. However, ultimately it is usually recommended that you seek professional advice when choosing a boiler size for your home. The team here at 247 Home Rescue can help you find a suitable boiler size for your home. Simply try our free online quote tool today or contact us on 0333 242 2524 for more information.

What Size of Boiler For 3 Bed House?

If you’re looking for a boiler for a 3-bedroom house, it is typically recommended for you to get a system that is between 28kW-34kW if you require a combi boiler. Boilers of this size range will usually be able to provide effective hot water to up to 15 radiators and between 1-2 bathrooms. If you plan on getting a heat only or system boiler installed, the ideal size of boiler needed is 18kW – 24kW.

For a more specific and bespoke recommendation of a suitable boiler size for your property, try our free online quote tool today.

A 28kw Combi Boiler Heats What Size of Home?

A combi boiler with 28kW of power will typically be an ideal size for a 2-bedroom home. A boiler of this size could also suit the needs of a 3-bedroom property if the heating and hot water requirements aren’t particularly high. A 28kW combi boiler could provide effective and efficient hot water to up to 15 radiators and up to 2 bathrooms.

Posted by: Martin Astley 23 May 2022