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What Size Boiler Do I Need?

Matt Robinson | Updated on April 20, 2020
What size boiler do I need?

Which boiler should I get? Which boiler do I need? We get asked these questions so frequently that we thought we’d offer some advice based on our years of experience.

The information offered here is simply a set of guidelines to help you get started. If you are considering replacing your boiler it’s essential that you ask a qualified installer to carry out a survey of your central heating and boiler system so that they can provide an accurate quote.

Our Gas Safe registered engineers are trained to work on …

Best for 1 & 2 bedroom

If you live in a 1 or 2 bedroom house, or apartment, with a single bathroom then you will probably be better off choosing a small combi boiler. Smaller properties, with up to 10 radiators, will typically need a boiler output of between 24-27kW.

Your property:

  • 1-2 Bedrooms
  • 1 Bathroom
  • up to 10 radiators

You’ll need:

  • Energy: 24-27kW
  • Approximate installation price: £1650-£1850 +VAT
Boiler Model Type Energy Approx Installation Cost
Worcester Greenstar 24i Junior Combi 24kW £1750
Vaillant ecoTEC Pro 28 Combi 24kW £1650

Best for 3 bedroom

If you live in a 3 or 4 bedroom house with a single bathroom and a further en-suite, with up to 15 radiators. you’ll have a wider choice of boiler based on your heating and hot water requirements. A higher capacity combi boiler with 28-34kW could potentially be the right choice and is a good choice is space is a concern. A conventional, or regular, boiler with a water storage cylinder might also be a consideration. Talk to use by calling 020 3880 5666 to discuss your requirements in more detail.

  • 3-4 Bedrooms
  • 1-2 Bathrooms
  • up to 15 radiators
  • Energy: 28-34kW
  • Approximate installation price: £1850-£2050 +VAT
Boiler Model Type Energy Approx Installation Cost
Worcester Greenstar 34CDi Combi 30kW £1950
Vaillant ecoTEC Plus 837 Combi 28kW £1850
Worcester Greenstar FS 30CDi Regular 30 £1850

Best for 4 bedroom

A larger 4 bedroom house typically has higher water and heating demand so will, therefore, require a bigger boiler. Combi boilers aren’t recommended for homes with more than 2 bathrooms because they don’t cope well with multiple hot water taps, including showers, being used at the same time. However, in some cases, a powerful combi boiler may be the right choice depending on your requirement and available installation space.

  • 4+ Bedrooms
  • 2+ Bathrooms
  • up to 20 radiators
  • Energy: 35-42kW
  • Approximate installation price: £2250-£2450 +VAT
Boiler Model Type Energy Approx Installation Cost
Vaillant ecoTEC Plus 438 Regular 38kW £2450
Worcester Greenstar 42CDi Combi 30 £2250
Bedrooms Bathrooms Boiler Size
1-2 1 24-27kW
3-4 2 24-27kW

Talk to our team for help and advice or to book

Call 020 3880 5666

Your call may be recorded for training or quality purposes