Boiler Size Calculator

Choosing the right boiler size is essential to save energy, ensure your heating system runs efficiently and keep your bills within your budget.

Boiler size means the output in kilowatts (kW), which is the amount of energy needed to provide your home with heating and hot water. If you install a boiler that’s too small, it may not provide enough heat and hot water for your family. Buy one that’s too large and you’re wasting energy and money.

So, how do you find out what size boiler you need in your home? Use our free Boiler Size Calculator below to get a quick estimate. It’s based on your heating needs and the number of bedrooms, bathrooms and radiators you have.

Boiler Size Calculator

Find the right boiler size by answering the questions about your home, then select the boiler type you want and click calculate to get your answer.

Why not try it now?

Boiler Size Calculator

What Size Boiler Do I Need?

As a general guide:

• Terraced houses or flats: 12-24kW
• Semi-detached or Bungalow: 24-30kW
• Detached home: 30-40kW

However, to find the ideal boiler type for your home, you do have to take a number of factors into consideration:

• The type of boiler
• The number of bathrooms and the hot water demand
• Number of radiators
• Property age and home insulation

Here’s a quick look at typical boiler outputs per property type, but remember, if you have underfloor heating or a large family, then you are likely to use more hot water than average, which means you may need a slightly bigger boiler.

Combi boilers usually need more power than system or regular boilers because of the fact that they supply hot water on demand.

Boiler Output vs Boiler Size

It’s easy to confuse boiler size with the dimensions of the boiler. But in this case, we are talking about the boiler’s energy output (kW) rather than the space it will take up in your home. You can have a compact boiler that has a high energy output; you don’t need to buy a boiler that takes up a lot of space unless that’s what you want.

Types of Boilers and Typical Sizes

There are three main types of boiler you can choose from; it’s important to assess the needs of your household so that your boiler matches those needs.

For example, if you have a large family and people are likely to use the showers at the same time, then you need a boiler that can provide strong water pressure even when more than one shower is being used.

Combi Boilers

• On-demand hot water, as the heating and water come directly from the boiler unit and not from a separate tank
• Energy efficient and space-saving
• Ideal for smaller homes
• Typical output – 12-35kW

System Boilers

• Uses a separate hot water cylinder which means you have to wait for the water to heat up, and then once it runs out, you need to wait 20 minutes or so for it to heat up again
• Ideal for homes with more than one bathroom
• Delivers strong water pressure even with simultaneous use
• Typical output – 18-30kW

Regular (Conventional) Boilers

• Has a hot water cylinder and a cold-water tank. Once the water is heated, it is stored in the cylinder, so you need time for the water to heat up
• Mostly used in older, larger homes with a standard central heating system
• Your home needs space for a hot water cylinder and a cold-water tank
• Best for homes with more than one bathroom in a larger household
• Typical output - 25-40kW

How Much Does a New Boiler Cost?

Boiler prices vary according to size, brand and the type of system you choose, but as a guide you’ll find:

• Combi boilers – between £525 and £2,950
• System boilers – between £1,150 and £2,800
• Regular (conventional) boiler - between £500 and £1,700

Installation Costs

The average labour cost to install a boiler is between £600 and £1,700. These costs will depend on factors such as ease of access, boiler location and whether you need extras like pipework or flue changes.

If you want your boiler in a different location, then an Extension Flue Pipe will cost between £75 and £125 per metre, and extra pipework and fittings can range from £400 to £600.

You might also decide to install a smart thermostat with your new boiler so that you can control your heating from your phone. The average cost of installing a smart thermostat is around £265.

Investing in the right boiler for your home will save you money on energy costs and ensure that you have an efficient heating and hot water system.

FAQs

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