Boilers are a range of sizes, not just physically but also in terms of their power output. Choosing the right size boiler for your home can not only save you money on your gas bills, but also ensure the quality of hot water and heating supplied to every room in your house, while preventing potential repairs that may be necessary from putting too much strain on a boiler that is too small. Here at K&M Maintenance we have over 15 years of experience with boilers; some may call us experts. So here is our guide to help you choose the right size boiler.

How many people?

The amount of people in your home is an important question as it relates to how much hot water will be required on a daily basis. More people means a larger boiler may be appropriate because of the hot water demands.

The size of the house

If your home is a terraced house, the chances are you will need a smaller boiler than someone in a large detached property. The larger the house, the more radiators there are to feed with hot water, and consequently, a larger boiler is necessary.

Scenario Guide

Many combination boilers come in three sizes, 24-27kw, 28-34kw, and 35-42kw. Below is a rough scenario outline for each boiler type:

A flat, apartment or small terraced house with one bathroom and less than ten radiators will need only a 24-27kw boiler to experience good hot water pressure and effective home heating.

A larger house with 3-4 bedrooms, up to 15 radiators and perhaps two bathrooms, a regular bathroom and an en=suite or a downstairs lavatory for example, would require a 28-34kw boiler.

Suitable for very large homes, bed and breakfast properties or hotels, with 20 radiators and more than 2 bathrooms, the 35-42kw boiler is most efficient when providing hot water to more appliances.


A well-insulated home will stay warm once the central heating system has been used, meaning that the boiler will not have to work as hard to heat the entire home, and less power will be consumed. Insulation types relevant to boiler efficiency include wall and roof insulation as well as double glazing.

If you are ready to choose a boiler, contact K&M Maintenance today for all your boiler advice, fitting and servicing requirements.