What size boiler do I need?
The right boiler size is about how much heat and hot water your home needs, not how big your house looks. A bigger boiler is not a better one, and an installer should work out the size for you after asking a few questions.
- A few quick questions
- No obligation
Boiler size means output, and it depends on your home and how you use hot water. Too small and the house struggles to warm up. Too big and it wastes fuel and cycles on and off.
What decides the size
Several things work together to set the right output:
- How many bathrooms and showers you have, and how often they run at once
- How many people live in the house
- How big the house is and how many radiators it has
- How well it holds heat, from insulation, windows and doors
- Whether you want a tank, or hot water straight from the boiler
Two houses with the same number of bedrooms can need quite different boilers.
Ways to work out your size
Guess from the old boiler
Match the output printed on your current boiler.
- Quick to do
- Free
- Your needs may have changed since it went in
- The old boiler may have been the wrong size too
Online calculator
Answer a few questions and get a rough figure.
- Gives you a ballpark
- Fine for getting started
- Cannot see your radiators, pipes or insulation
- Different calculators give different answers
Ask a national call centre
Give the details over the phone to someone who may never visit.
- Easy to arrange
- May not know your area or your type of home
- Often a script rather than a conversation
Tell us about the job
Answer a few questions on the quote form and we price it.
- A written price before any work starts
- No obligation to go ahead
- A local installer, not a national call centre
What to have to hand
- The make and model of your current boiler, if you can see it
- How many bathrooms and showers you have
- How many people live in the house
- How many radiators you have
- Whether you have a hot water tank or cylinder
- Whether the house is a flat, bungalow or larger home
- Any plans to extend or add a bathroom
Common sizing mistakes
Do
- Think about how many taps and showers run at the same time
- Mention any extension or new bathroom you are planning
- Ask the installer why they chose that size
- Compare like with like when you get prices
Don't
- Assume a bigger boiler is always better
- Copy the old boiler without checking it still suits
- Size by the number of bedrooms alone
- Pick on price before you know what is being offered
Examples of boiler installations
Example images of the style of work, not photos of our jobs.
How it works
Get my price- 1
Tell us about the job
A few quick questions about your boiler and what is going on.
- 2
Get your price
A written price before any work starts.
- 3
We do the work
We do the work you agreed.
Related
Where we work
Aylesbury and the areas around it. Every postcode listed is in our area.
Boundaries: Office for National Statistics (OGL v3.0). Contains OS data © Crown copyright and database right 2024.
Want it sorted for you?
Tell us what's going on and we'll price the job.
- A few quick questions
- No obligation