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What Size Electric Boiler do I Need?

Nick Geary
By: Nick Geary
Updated: 25th October 2023

Electric Boiler Size

The size of an electric boiler is measured in kilowatts and it’s an indication of power rather than physical size.

Follow the advice in this guide to ensure that you install an electric boiler that will be able to meet your home's demand for heating and hot water.

If you’d like tailored advice on getting a new electric boiler, then we’d recommend contacting a professional heating engineer near you. The best heating engineers will also be able to offer you a personalised quote so that you know exactly what you’ll be paying.

Boiler Guide can help connect you with up to 3 trustworthy heating engineers near you. It’s as easy as answering a 1-minute form and just relaxing while you wait for an installer to offer you a personalised quote.

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How do electric boilers work?

An electric boiler provides central heating and hot water to a property just like any other boiler type. The difference however being that electric boilers don't have to burn a fuel, such as gas or oil:

  • No need to store the fuel (LPG and oil)
  • No chance of a carbon monoxide leak
  • Electricity is readily available

There are 3 types of electric boiler suitable for domestic installation and the way the unit works depends on the type of electric boiler:

  • Direct: Heats water on demand
  • Storage: Includes a hot water cylinder either within the unit or elsewhere around the property.
  • Dry Core Storage: heat bricks overnight (allowing you to make the most of cheaper nighttime energy tariffs). This heat is then released into water for central heating and domestic hot water during the day as and when needed.

Homes best suited to an electric boiler

Electric boilers are best suited to smaller homes and flats as they can't meet the high central heating and domestic hot water demands of larger homes. Plus, electric boilers don't take up anywhere near as much space as gas and oil boilers, making them even more ideal for smaller homes.

If your home has more than 1 bathroom, then an electric boiler is unlikely to be able to meet the demand for hot water. In this case, it's recommended to turn to an alternative fuel such as gas.

What size electric boiler do I need?

The power output of a boiler is measured in kilowatts (kW) and helps to give an idea of the level of heating and hot water demand the boiler will be able to meet. Simply put, the higher the kW rating, the more radiators and taps it can supply at any one time.

Electric boilers don’t tend to be very powerful, which is why you won’t see an output rating much higher than around 15kW. Gas and oil boilers, on the other hand, can have a much higher output rating making them much more suitable in cases where heating and hot water demands are higher, like for larger properties. Make sure to check out our best boiler for 3 bed housebest boiler for 4 bed house and best boiler for 5 bed house guides for more information regarding property size.

As a general rule, add up 1.5kW per radiator around your property. So, if there are 8 radiators then a 12kW electric boiler will provide sufficient central heating.

Number of Radiators Output rating
4 6 kW
6 9 kW
8 12 kW
10 15 kW

Which electric boiler should I install?

Using the table above, you can get an idea of the ideal electric boiler size for your home. Once you know the output rating you're looking for, we've listed some electric boiler models below to help you find a unit with the output rating that you need.

Find out more about these units in Best Electric Boilers.

Manufacturer Model Available Outputs (kW) Dimensions (HxWxD) Potential Cost
Electric Heating Company Comet Combi Boiler 9, 14.4 1745 x 580 x 630mm £2,571
Heatrae Sadia Electromax 9, 14.4 1745 x 580 x 630mm £2,571
Elnur Mattira MAC15 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 830 x 555 x 450mm £1,750 – £2,000
THERMAflow Electric Combi 10, 11, 13, 14, 16, 18 From 1590 x 550 x 690mm up to 1920 x 710 x 850mm £2,360 – £4,050
Electric Combi Boilers Co. Elektra EK.C 12 875 x 400 x 300mm £1,190
Ferroli LEB TS 6, 7.5, 9, 12 740 x 440 x 265/340mm Unknown

Have you found an electric boiler that suits your home? The next step is to get quotes to compare and choose the best deal. The easiest, fastest, and most reliable way to do this is by using Boiler Guide’s free quote service.

By taking less than a minute to answer a few simple questions, you can get up to 3 quotes from trusted installers near you. Any quotes you receive are free and come without any obligations.

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What if the electric boiler is the wrong size?

Install a boiler with an output rating that's too low and the unit will struggle to meet the heating and hot water demands of your home. Likewise, have an electric boiler that's too powerful installed and your energy bills could soon begin to rise.

This goes for all boilers, not only electric boilers, which makes finding a boiler with the most suitable output rating for your home essential.

If you're at all unsure or need any help about the boiler size needed for your home, the best thing you can do is to contact a heating engineer to assess your property.

At Boiler Guide we offer a portfolio of more than 5000 Gas Safe registered engineers across the UK. All of these heating engineers are professionally accredited and highly rated by our customers. See the latest reviews of our engineers here: https://www.boilerguide.co.uk/customer-reviews

What about the physical size?

As well as the size of the boiler in terms of power, you might want to know about its physical dimensions too. More often than not, electric boilers are smaller than gas and oil boilers so won't take up as much space.

Installation is also more flexible as they can be installed on just about any wall, whereas gas and oil units need to be on an external wall so that waste gases can be expelled out of the property.

How much do electric boilers cost?

Electric boiler costs vary depending on the model and manufacturer. As you might expect, the smaller models will often be the cheapest with a price tag of around £1,500 stretching up to £2,500 for the larger models.

As well as the cost of the electric boiler itself, you'll need to consider the installation too. Again, installation costs will vary from installer to installer so we highly recommend comparing multiple quotes.

Using Boiler Guide, you can get free quotes from up to 3 fully-qualified electric boiler installers based in your local area. Why 3? Well, if you were to only get the 1 quote then you wouldn't know if you're getting the best possible price. Getting 3 quotes on the other hand will increase your chances of finding the best price from the most reputable installer.

Start getting electric boiler quotes by clicking the button below.

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Electric boiler running costs

Once the electric boiler has been installed, your attention will turn from the upfront costs to the running costs. It's well known that electricity is expensive and that's only proven by comparing it to gas.

The price you pay for electricity is different depending on your tariff and the area you live. In the UK, the average price of electricity per unit is 14.4p/kWh, while gas is only 3.8p/kWh. While that is quite a difference, gas isn't an option for every home, fortunately, there are several ways to reduce those running costs:

  • Switch to an Economy 7 tariff that offers reduced rates for electricity during the night
  • Generate free renewable energy by installing solar PV panels
  • Heat water stored in the hot water cylinder for free with solar thermal

Not only are there ways to keep the running costs down, savings can be made in other areas with an electric boiler compared to other boiler types:

  • Installation is often cheaper
  • No need for an annual service
  • Very few moving parts mean there's less chance of a fault developing saving you from large repair bills

We compared the total cost of an electric boiler with a gas boiler over 10 years to find out which works out cheaper in our article Gas vs Electric Boiler.

What are the benefits of an electric boiler?

Find an electric boiler with the right output rating for your home and you'll benefit in a number of ways once it's been installed.

  • There's no need to arrange an annual service which will save you money
  • No risk of a carbon monoxide leak
  • Quiet in operation
  • Small in size so won't take up too much space
  • Greatly reduce the carbon footprint of your home
  • Installation is more flexible and often cheaper as there's no need for a flue or condensate pipe

In order to maximise electric boiler benefits, it’s important to have a trustworthy and reliable engineer installing your new boiler. An incorrectly installed or inefficient electric boiler can lose you hundreds of Pounds a year. That’s where Boiler Guide comes in.

Boiler Guide connects homeowners looking for new boilers with up to 3 trusted boiler installers from our partner network. We’ve vetted all of them to ensure they have updated qualifications and are Gas Safe registered. That way, you know you’re in the best hands. Each installer will offer you a personalised quote tailored to your situation.

If you’re ready to take the next step towards getting the best deal on installing a new electric boiler, then click the button below, answer a few questions, then just wait to be contacted by our team.

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Nick Geary

About the author

Nick Geary

Nick has a wide range of experience writing about conventional and renewable heating solutions, and is always increasing his knowledge by researching any new heating technologies on the horizon.

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