What Size Boiler Do I Need?

Types of Boiler For Your Home

Perhaps the biggest factor in choosing a new boiler is the type of boiler you choose to have. There are three main options available for those using mains gas:

Combi Boilers

Combi Boilers combine heating and hot water in a single unit. They generate hot water on demand meaning there is no need for a hot water cylinder.

Ideal for:

• Flats
• Apartments
• Smaller houses

Regular Boilers

Regular boilers provide heating directly from the boiler and work with a hot water cylinder.

Ideal for:

• Large flats
• Large Apartments
• Medium/Large houses

System Boilers

System Boilers are heat-only boilers that work with a hot water cylinder but with an integral pump and diverter valve.

Ideal for:

System boilers tend to only be found in new build homes.

Other Types of Boilers

• Oil Boilers
• LPG Boilers

Ideal for:

Oil and LPG-powered boilers tend to only be used in properties where there is no mains gas supply available. This is because the running costs of these boilers will generally be higher.

These days, most people are looking to have a combi boiler installed unless their home is too big for one. So, for the purposes of this guide, we have focused on combi boilers.

Understanding What Size Boiler You Need For Your House

Some boiler manufacturers will offer a handy boiler size calculator tool on their website. Unfortunately, not all do. Ideal Boilers is a prime example. So, if you need some help, we are here for you.

There are three major groups of combi boiler sizes:

1. 24kW – 27kW
2. 28kW – 34kW
3. 35kW – 42kW

And typically, you can estimate the kw boiler size needed using this as a ball park.

Boiler Sizing Chart

This all assumes that there is a reasonable demand for hot water, and nothing excessive.

Combination boilers heat hot water as and when it’s needed. So, no hot water is stored.

Boilers will always give priority to your hot water. So, if you jump in the shower for 10 minutes, some of the output directed at the central heating will likely be pushed towards the shower. If this isn’t a problem (which it isn’t for most), a combi boiler will fit your needs perfectly.

Also, this assumes you have average-sized radiators. If you have large radiators (such as a 500mm x 2000mm double convector) as part of your central heating, you’ll likely need a higher output boiler than the onesmentioned in the above table.

Boiler Recommendations

So far, we have outlined how you can determine the right sized boiler for your property. But having done this, which boiler is the best for you?

This is a subjective question and the right boiler for you will depend on a range of things including your budget, the length of warranty you want, and where you decide to buy it from.

But in this section, we will reveal our recommended boiler makes and models suited for different sized properties:

Boiler size for a small 1-2 property with up to 10 radiators (including apartments and flats)

• Worcester Bosch 25SI Compact (prices start at £1,795 with HEATABLE) Viessmann Vitodens 050 (prices start at £1,695 with HEATABLE)
• Ideal Logic Plus 24

Boiler size for a 3-bedroom property with 10 radiators

• Worcester Bosch Greenstar 25i or 30i
• Viessmann Vitodens 050
• Ideal Logic Plus 30

Boiler size for a 4-bedroom property with 14 radiators

• Viessmann Vitodens 100
• Worcester Bosch Greenstar 42CDI Classic
• Ideal Logic Plus 35

Boiler size for properties with 5 or more bedrooms, with more than 16 radiators

It is possible to use a combination boiler for larger properties with this number of radiators, but calculations need to be made beforehand and we would recommend getting a qualified heating engineer to visit your property to sizer things up and make a recommendation. Typically, properties of this size will have a system boiler feeding a hot water cylinder that stores water, but this can vary from one property to another. Our Conclusion About Boiler Size

Getting the right sized boiler for your property is important and in this guide, we have provided all the information you will need.

You can get a good idea of the right sized boiler for your property by using an online calculator. We recommend trying HEATABLE as their calculator will also point you in the direction of some great deals as well.

We have also outlined some others and detailed how to choose the right-sized boiler depending on the number of radiators and the size of your property.

We have also suggested some of the best combi boilers currently available for different-sized properties.

Still got questions relating to which size boiler is right for your home? Any other tips for our readers we haven’t covered in this guide? Please share your thoughts with us using the comment box below.