Everything you need to know about gas boilers and smart heating.

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When your boiler decides to give in for good, the feeling of the unknown can become very daunting. Our team have carefully created this guide to give you an in-depth insight into our boiler world. Helping you make the right decisions, at the right price! 

Your first challenge is working out which type of boiler you have. Use the table below to identify yours.

What type of boiler do I have?

Don't worry if you cant work out which boiler you have. Email some pictures over to our team and they will happily identify your boiler for you and for FREE! 


What size boiler do I need ? 

Once you know what type of boiler you have, you then need to work out which size boiler you require. If you have a combi boiler then this is relatively easy, for a system and regular boiler you will need a calculator to hand. 

Combi Boiler Size Guide

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System and Regular Boiler

Sizing Guide

Sizing a system or regular boiler is slight more difficult. We need to calculate the total heat requirement for your home by recording the total output required for your radiators and hot water cylinder. 


The way we calculate the heating requirement is by working out the BTU's (British Thermal Unit) for each radiator. For this you will need to download a but calculator app, or use the following guide.

Use the following three radiator sizes and bunch your radiators into the closest size to get your required BTU;

Height: 600mm   

Width:  600mm

Single Convector:  2100Btu

Double convector: 3600Btu

Height: 600mm   

Width:  1000mm

Single Convector:  3000Btu

Double convector: 4000Btu

Height: 600mm   

Width:  1400mm

Single Convector:  5000Btu

Double convector: 6000Btu

Once you have calculated the Btu total for all your radiators, you will need to do a quick conversion to kilowatts (Kw). This can be done using the example formula below;

Total Btus example : 60'000 

60000 divided by 3412 = 17.58 Kw

Rounded up, this gives you a requirement of 18kw for heating system. 

Hot Water

To calculate your hot water requirement you will need to start by measure your copper cylinder or look at your unvented cylinders databadge. This will give you an indication of the size of your hot water cylinder. 

The size of hot water tank will vary between houses depending on the demands of each house. For the example, we will use a 120 litre tank. 

In the UK, mains cold water is usually assumed to be 4 degree celsius, whilst 'hot water' for a domestic home is usually set around 60 degrees celsius to avoid scalding. So the cold water needs to be raised by 56 degrees celsius within the hot water cylinder. 

As 1 litre of water needs approx. 1.16 watts to raise it 1 degree celsius in 1 hour, a 120 litre tank of cold water needs a total energy input of approx. 7800 watts per hour to heat the tank to its required 60 degrees celsius. 

Example formula (120 x 1.16 x 56) 7795 watts

Therefore if you have a 120 litre tank, your hot water requirement is 7.8Kws. If you had a 300 litre tank, your requirement would be 19.5Kws. 

You now have a heating requirement of 18kw and a hot water requirement of 7.8Kw. Rounded up, this means you need a boiler with at least 26Kw output. 

You are now ready to move on and pick your controls.

Don't worry if you cant work out which size boiler you have. Email some pictures over to our team and they will happily identify your boiler for you and for FREE! 


What controls does my boiler need? 

Choosing what controls your boiler can be as simple or complicated as you want it to be because, as with most things, boiler controls have gone smart too. The choice of controls available vary from the standard pin dial and on/off switch on the boiler face to a 'Nest learning thermostat' which you can control from your smartphone. 

See some popular options below

Don't worry if you cant work out which boiler controls you need. Give our team a call and they will be happy to talk your free the different options to suit your requirements and budget. 

How much does it cost to install my new boiler? 

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Now for the most important question, how much is your new boiler going to cost? Our team have carefully created the below table to give you an indication of costs. 

If you still need help picking, choosing or working out which boiler you have, need or want replacing, please feel to give our new boiler team a call, its what they are here for. 

Its easy to replace your boiler with us!

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