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How to work out what size combi boiler you need for your home?

Installing a combi boiler is an increasingly popular choice for many UK homes. As they heat water directly from your mains, they provide an unlimited amount of hot water on demand. They are a great space-saver too, as they do not require a separate hot water cylinder or header tank. This also makes them exceptionally energy efficient, as you only heat the water you need, and do not waste energy when storing hot water for later use. However, there is no one-size-fits-all perfect boiler for your home, so making sure you have the right size boiler is important when you are looking for a replacement.

Why are boiler sizes so important?

The power of your boiler reflects how much hot water it can produce and how much heat it can supply to your radiators to keep your home warm and is measured in kilowatts (kW). 

Number of hot water outlets

The first consideration for how large a combi boiler you need,is how many hot water outlets you use at the same time in your home. Combi boilers can typically produce between 9 litres and 16 litres of hot water per minute. Because a large amount of power is needed to instantaneously heat hot water,even quite small combi boilers can potentially heat a large home. However, you don’t have to worry about your boiler being overpowered as it will step down the number of kilowatts being produced, to match the heating demand from your radiators. 

If you live in a home where more than one person is likely to be having a shower or filling a bath at the same time, or you want a very powerful shower, then you need a boiler that produces more litres of water per minute.

How strong the water pressure is in your area

As combi boilers heat hot water directly from the mains, they can never send more litres a minute of hot water to your shower or bath than is being supplied to the home from your water company.  So, there is no point installing a very powerful combi boiler that can heat more water than the mains can supply it with. If your water pressure is very low,then a combi boiler probably isn’t for you, and you need to consider a regular or system boiler. 

How large is your home and how well insulated is it

As we have already said hot water is the first consideration when sizing a combi boiler, but you still need to check if it is big enough to heat your home particularly if you live in a larger property or one that is very badly insulated. 

If you have a large home but it is well insulated, and your central heating system has been designed with large radiators that just have to be comfortable warm to keep your home nice and snug, you might not need as powerful a boiler as you think. Conversely, a smaller poorly insulated home, with relatively small radiators in each room which have to be kept very hot to warm the house, could possibly need a more powerful boiler. 

While these factors should help you get a rough estimate of what size combi boiler is right for your home, you should always get an expert view before committing to a purchase. Fortunately, you can take a short online survey to find out which boiler size is right for you, with a no-obligation quote so you can understand how much it would cost.

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