Fitting the right boiler for your home is extremely important, you need to find a boiler that is just right for your home. A boiler that is too small will not be able to heat your home adequately or produce enough hot water. A boiler that is too big will produce more heat than needed which will increase bills, waste energy and produce unnecessary emissions.

Neither is a great way to live, so how do you find the solution?

How to calculate the right size boiler for your home.

The size of a boiler, also known as output, is measured in kW. This means, the higher the number the better the supply of hot water, but this doesn’t mean you should be buying the highest output available. Generally, boilers range from 24kW to 42kW in size.

There are a few things to consider when choosing the right size boiler for your home:

Current boiler size

It’s a good idea to know the size of your current boiler but don’t assume you need to stick with the same size going forward. Several things may have changed since it was installed such as the household’s water demands, the level of insulation or the addition of an extra bathroom. Or you may have plans for the near future such as loft conversion or an extension.

If your home is regularly running out of hot water, it could mean that your current size of boiler is not up to the task and you need to think bigger. However, if your boiler is more than 8 years old, it may just be a case of inefficiency rather than a lack of capacity.

Size of your home

Usually the more radiators and bathrooms you have the higher the output of your boiler will be. You should also be aware of the size of the area that you are trying to heat. It is worth taking into consideration that an electric shower doesn’t reply on a boiler for hot water so doesn’t need to be included in any calculations.

For example, if you were interested in having a Combi boiler fitted, here is a rough sizing guide:
24-27kW – small house (1-2 bedroom) or flat, up to 10 radiators, 1 bathroom
28-34kW – medium house (3-4 bedroom), up to 15 radiators, 1-2 bathrooms
35-42kW – large house (4 or more bedrooms), up to 20 radiators, 2 or more bathrooms

Hot water demand

Most replacement boilers that are fitted are Combi boilers, which heat water on demand so there’s no waiting around for the water to heat up. However, this does mean that you need to give some thought as to how much hot water your household gets through on average per day. If you have lots of showers, baths or sinks running at the same time then a Combi boiler may struggle to cope with the demand.

How else can I make my home as cosy as possible?


If your home isn’t insulted fully there could be a risk that you are losing a lot of heating through the roof, walls, floors or windows. To help give your heating system the best chance to do its job, you should think about investing in more efficient insulation techniques.

Smart Controls

Controlling your boiler has become easier than ever and it’s now possible to adjust the temperature of your home from any location via smartphones or tablets allowing you to reduce the amount of energy you waste. Some can even automatically compensate for the weather outside.

Annual boiler servicing

To make sure your boiler is running at its best for as long as possible, it’s important to get it serviced by a professional on an annual basis. This allows for problems to be caught early before they develop into long term damage.

Speak to a professional

Our friendly and fully qualified engineers will be able to advise you on the right size boiler to suit your lifestyle and your household.
Contact us today on 0114 272 2586.