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What size boiler do I need?

What size boiler do I need?

Whilst it is useful to have an idea of the size and type of boiler suitable for your home, you should always enlist the help of a heating professional. New boilers are a large investment and are responsible for providing your home’s heating and hot water needs. With the right type and specification of boiler you should expect at least 12 years continuous use before the need to start considering a replacement.

Boiler sizes explained

Boiler size does not typically mean the physical size but the output of energy (heat) produced by the boiler.

This energy output is measured in kilowatts or kW as it is displayed. Boilers come in a range of outputs, the type pf boiler you require will depend on your home and family needs.

Often people will search for ‘best boiler for a 4-bedroom house’ or ‘2 bedroom semi-detached’.

However, this is not how boiler size is typically calculated.  Your surveyor when calculating your boiler size will look at the number of radiators in your home, amount of bathrooms and your individual family needs. Simply put the more heat and hot water you require the higher the kW needed.

It is important for you to think about your homes heat and hot water usage. For example if you are planning on having an extension you may wish to invest in a more powerful boiler.  This will ensure the boiler can cope with the additional radiators and/or bathrooms that you plan to add.

If your boiler is not sized correctly for your home one of two things can happen;

  • Undersized boiler. This can result in a shortfall in the amount of heat generated for your home or not enough hot water is generated or in some cases both.
  • Oversized boiler. If your boiler is overpowered you can end up spending a much higher upfront cost of the boiler than needed.

What size boiler do I need?

There is not a one size fits all for boilers, but as a rule of thumb you can group boiler sizes into three main groups.

Apartment / flats / houses with 1-2 bedrooms, 1 bathroom and up to 10 radiators

  • 12kW – 18kW

Apartment / flats / houses with 2-3 bedrooms, 1+ bathrooms and up to 15 radiators

  • 18kW – 24kW

Larger houses with 4+ bedrooms and 2+ bathrooms and over 15 radiators

  • 24kW – 42kW

Other factors to consider

During your home survey our heating surveyor will also look at the age of your property and the insulation levels.  For example, older properties typically have poorer insulation levels compared to a modern properties. Furthermore double glazing and roof / loft insulation all have a bearing on heat loss and hence kW needed.

Need more help?

To arrange a free of charge boiler survey at your home, why not give our friendly office a call on 01258 472132 or fill in the enquiry form.


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