• Get the best quotes, fast!
  • Over 5,000 engineers across the UK
  • Gas Safe registered engineers

Need a New Boiler?

Get FREE no-obligation quotes now!

  • No delays! Get quotes today
  • Compare quotes & get the best prices
  • Gas Safe & OFTEC registered engineers
 4.8 stars

1,567 reviews

 4.8 stars

1,567 reviews

What Size Electric Boiler do I Need?

Nick Geary
By: Nick Geary
Updated: 6th July 2022

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.

Get Free Electric Boiler Quotes

Get quotes to supply and fit a new boiler now.


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.

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.

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

Find out more about these units in Best Electric Boilers.

Get Free Electric Boiler Quotes

Get quotes to supply and fit a new boiler now.


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.

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.

Get Free Electric Boiler Quotes

Get quotes to supply and fit a new boiler now.


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.

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 cyclinder 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 Electric Boiler vs Gas Boiler: Pros, Cons & Running Costs.

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

Get Free Electric Boiler Quotes

Get quotes to supply and fit a new boiler now.


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.

Need a new boiler?

Get FREE no-obligation quotes now!

Excellent 4.8 out of 5

Find local heating engineers

Find approved boiler engineers
in your area.

Begin your search by entering your postcode below.