What size boiler do I need for my property


It is difficult to define which size boiler you will need for your property.  You can, however, work out approximately what size boiler you will need based on some basic information.  The size of the boiler is known as the output also.  It is measured in kilowatts (kW) and usually the higher the number of kW the more powerful the boiler will be.  You find that domestic boilers will range from 24kW to 42kW.

ChoosingThe Right Size

According to Andy from Homeglow Gas Services, “A boiler too small will not be able to heat your home sufficiently or be able to produce enough hot water for your property.  A boiler that is too big will obviously use more fuel and your energy bills will be higher and more expensive and making your carbon emissions unnecessarily high too.”

Instead of thinking of how many bedrooms your home has and working out the size of the boiler from that, installers will consider factors like how many radiators are in the home and how many bathrooms and how many people live in the home.

There are some general guidelines to consider though which you can look at to decide the right size boiler for you.

Combi Boilers

A Combi boiler which has an output of around 24-27kW is best suited to a small terraced house or a flat or a home with 1-2 bedrooms.  It will run up to 10 radiators and supply hot water for 1 bathroom.

A Combi or System boiler has an output of around 28-34kW is best suited to a medium terraced house or a semi-detached property.  It will run up to 15 radiators and supply hot water for 2-3 bathrooms.

Regular Boiler

A System or Regular boiler that has an output of around 35-42kW is the best one for a detached house or large semidetached house.  It will run up to 20 radiators and supply hot water for 3 or more bathrooms.

If you have 2 or more bathrooms that need hot water at the same time, then a Combi boiler may struggle to provide this.  A professional engineer may recommend that you install a System or Conventional boiler sized between 35-42kW depending on the hot water you need at one time.  These heating systems include a hot water storage cylinder which means you have multiple taps, baths and showers can be supplied at the same time with no loss of pressure.  Electric showers do not rely on the boiler for hot water, so this does not have to be included in any calculations on which boiler to get.

Don’t Go On Your Current Boiler

It’s a good idea to know the size of your current boiler system in your home.  But do not presume you have to have the same size boiler again as things may have changed since it was installed.  These factors could be the households water demands have gone up or down and you may have had an addition of an extra bathroom.  If your home is regularly running out of hot water, it could be a sign that your current size boiler is not up to supplying it and you need a bigger boiler.  Although if your boiler is over 8 years old it could also be it is running inefficiently.

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