Electric Boilers / Electric Central Heating Boilers – 0.5kW to 45kW

Electric Boilers – With over 2 million homes in United Kingdom at present are without a mains gas network supply, also many older houses have flue restrictions or are listed buildings that prevent the use of a gas or oil boiler on site. In these situations an electric boiler can be the perfect solution to your central heating needs.

Electric Boilers – What are they ?

Electric boilers can be installed in small to medium sized flats or houses to produce the hot water for both your heating system and domestic hot water use ( normally via a indirect cylinder for your domestic hot water requirements). The most commonly installed boilers either use gas or oil to heat the water, an electric boiler will heat the water via an electric element or multiple elements. They are a popular choice for flats and homes where gas is not an option and oil is either impractical or too expensive. They tend to be limited limited as to the amount of Domestic Hot Water (DHW)  they can produce instantly therefor we always recommend using an indirect hot water cylinder for the domestic hot water, especially if the property has a bath fitted.The smaller boilers , i.e. from 0.5kW to 15kW outputs the electric boilers are available in 240 volt , Single Phase , after 15kW the units require a Three Phase power supply.They are often fitted in new build homes and flats as they are cheaper to install and maintain. Also, with no gas emissions, they are seen by many as a more environmentally friendly choice, as the electric power supplied can be from renewable sources such as wind, solar or tidal electric production.

Advantages of Electric Boilers


Can be integrated with PV panels to yield further energy savings

Cheap to buy as Electric Central Heating Boilers have no gas valve, fan, air pressure switches, Ignition PCB’s, Ignition leads, electrodes, or burners which keeps the cost down

No yearly servicing is required

No yearly Gas Safe Certificate in relation to rented properties

Cheaper to install

Installing an electric boiler is simpler than gas or oil and so is quicker and cheaper , also as there are no waste gases an electric boiler doesn’t need pipes, flue or chimney so the installation of the boiler will cost you less.

Does not require an external wall for mounting the boiler

High efficiency

As electric boilers don’t need to burn fuel to produce heat they don’t lose energy through waste gases or flues. In many cases this results in efficiency rates of 99% compared to 89 – 95% for most gas or oil boilers


Electric boilers are almost completely silent as there are no moving elements within the boiler

Light and compact

They lack waste gases and thus any flue / chimney means the unit is much more compact and light ensuring you have more flexibility about where in the property you have it installed.This makes them much more versatile in terms of where they can be placed in the property.

Easier to maintain

No annual landlord gas safety certificate is required

Unlike gas and oil boilers which have more mechanics included, electric boilers don’t need annual servicing to keep them functioning


No carbon monoxide threat to the people within the property

No CO detectors are required

Totally safe when the boilers are protected by RCD & MCB

No condensate pipes to freeze up

Electric Boilers – Things you need to Consider and Know

The biggest and most important issue with electric boilers is not the boilers themselves, it is the power that they require to operate

Firstly you need to –  What’s the difference between a single-phase or three-phase electricity supply ?

Both of these are electricity supplies, it’s the amount of power that is different. A single phase supply is smaller than a three phase supply meaning you cannot use as much power. A typical house will need a single phase supply whilst a larger house, blocks of flats or commercial building will need a three phase supply.

The way to tell what supply a property has is by looking at the fuse on the service head. Single-phase has one 100 Amp fuse ( Although in some older properties this may be a 60 Amp fuse, bit it’s quite rare ) and a three phase supply has three 100 Amp fuses.

So a UK home typically has a 100 Amp supply fuse , this means that all the home electrical appliances , whilst being used simultaneously should not draw over 100 Amps , otherwise the fuse can blow.

Following is a chart showing the electrical ratings of commonly used household appliances –

Firstly Electric Showers- these can have some high loads

Standard Shower Rating Watts (kW)          Maximum load from the supply (Amps)

6kW                                                                      26

9kW                                                                     39.13

9.5kW                                                                  41.3

10.5kW                                                                45.65

11.0kW                                                                47.82

Domestic Portable ApplianceAmps UsedWatts Used
Laptop<0.565 – 100
Mobile phone charger<0.5<12
Satellite TV box<0.530
DVD player<0.528
Hair dryer10.02200
Landline cordless telephone charger<0.510
Computer monitor<0.5100
Desktop computer3.0700
Television 42″ HD0.5120
Games console0.86<200
Washing machine102200
Tumble dryer11.02500
Vacuum cleaner9.02000
Radiator (oil filled)13.03000

So why does this matter ? Well it matters because the larger the electric boiler you go in size , the more Amp’s you need available to power the boiler . You will generally find that in a standard 100 Amp – 240 Volt , single phased supply property , the largest boiler you can use is a 10 kW Boiler ( now a 15kW boiler-see the update below in red ) – why ? because this boiler will draw 45.5 Amps , which is getting close to half of the supply for a standard UK property , even when you consider a diversity factor ( which in layman terms means that not every electrical appliance would be on at the same time ) you are starting to possibly exceed your supply and tripping out fuses etc.

UPDATE – We have now solved this common problem 

We now do a new range of electric boilers for central heating and / or domestic hot water, designated the “FHEL” range that can now utilise what we are calling the ” maximum current watcher” – it is basically a releasing relay (restriction of current). The relay monitors and controls the electric voltage in the whole house or flat and in the case of exceeding the permitted values of the electric current it reduces the input power of the electric boiler. All of this is done automatically, without any human intervention needed.This system will not only operate on our 240 volt / 1 Phase Electric boilers , but also our 400 Volt / 3 phase units as well. This now means that you can use our 15kW electric boiler model, in a property or flat with standard 240 volt, single phase with no worries or problems that the unit will trip out the main electric board.

OK what can I do about it  ? Well the best solution would be to get your electrical supply upgraded to Three Phase – Is it possible  / How much is it to do this ? I don’t know , we just supply the boilers – please contact UK Power Network , who are responsible for this here

Or another option may be to get a second 100 Amp supply to your property – Again , contact UK Power Network on the link above – this option may well work out cheaper than having three phase supplied to your property, but again don’t contact us about this, we just supply the electric boilers and this is not our remit.

Electric Central Heating Boilers – The Standard Range 

The Standard Series of electric Central Heating Boilers -The standard range is available in 7.5kW,15kW,22.5kW,30kW,37.5kW and a 45kW Output models. This electric central heating boiler range goes from 2.5kW to 45kW of Heating Output. These Electric Central Heating Boilers work up to maximum temperature of 80°C and minimum pressure of 0.5 Bar to maximum pressure of 3 Bar.The feature the following benefits –

  • Option to produce domestic hot water via an external indirect cylinder / calorifier and 3-way valve
  • An inbuilt energy saving pump ErP compliant heating pump
  • Very quiet operation due to selected switching relays
  • Fluent regulation ( boiler output ) in low steps of 2.5 kW for the electric boilers up to 30kW, and 5 kW for the electric boilers from 30 kW to 45kW
  • Option to connect the boilers to an  OpenTherm+ thermostat or controller e.g. a nest controller etc ( control your electric boiler on the go, from your phone)
  • Compensated weather control option for boiler – i.e. control / output according to the spatial or outdoor temperature ( a great energy saving feature)
  • Option to connect up to 32 boilers in an intelligent cascade boiler configuration, in order to have increased heating power or output
  • Outputs of up to 15kW, when using a 240 Volt / 1 Phase electrical supply – and up to 45kW when using a 400 Volt / 3 Phase electrical supply ( up to 1,440 kW when used in a cascade electric boilers configuration)
  • All of these electric central heating boilers up to 23kW Output have an inbuilt 7 litre expansion vessel inbuilt, after this size the electric boilers must use an externally mounted expansion tank dependant on system volume and temperature.
  • Option of remote boiler control through SMS messages when fitted with the SMS module
  • Option to monitor the maximum current drawn to prevent overloading of the consumer board in the building/property – this system reduces the input power to the electric boiler automatically – ensuring that your main fuse does not blow.
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Electric Central Heating Boilers – Standard Series From Flexiheat UK

Standard Series – Electric Central Heating Boilers – Technical Data

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Electric Central Heating Boilers – Standard Series- Technical data – Flexiheat UK

Electric Boilers- with touch display

The next option in the Flexiheat UK electric central heating boiler product portfolio is the touch screen range.This range of electric central heating boilers, are available in three sizes – a 4.5 kW output electric boiler, designated the FHEL5, a 9kW output electric boiler , designated the FHEL9 , and the largest unit being the 13.5kW output electric boiler,which is designated the FHEL14.All of this range are suitable for a single phase – 240 volt supply or can also be wired from a three phase -400 Volt supply.This range of electric boilers has all the features of the standard series , with a few notable enhancements,these being –

  1. Simple and intuitive control of the boiler ,due to the well arranged touch display
  2. Fluent regulation in low power output steps by 500 Watts (0.5kW) for the FHEL5 model, by 1,000 Watts (1 kW )for the  FHEL9 model ,and 1,500 Watts (1.5kW) for the FHEL14 model.These lower power outputs ensure that the heating load requirement is appropriately matched. and brings even greater heating efficiency to the wet central heating electric boiler system.
  3. Minimum output of the electric boilers is 500 Watts (0.5kW) for the FHEL5, 1000 Watts (1 kW ) for the FHEL9,and 1,500 Watts  (1.5kW) for the FHEL14 models , which all helps to increase the efficiency of the electric central heating boiler system.
  4. Due to the low minimum performance and the modulation option, these boilers are recommended for low energy houses and passive houses ( ultra low energy buildings )
  5. The modular digital control assures optimal operation of the electric boiler in a way that optimizes electric energy consumption with the rated thermal output of the electric boiler.
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Electric boilers for central heating – “FHEL” Touch Screen Series from Flexiheat UK

Touch Screen Series – Electric Central Heating Boilers – Technical Data

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Electric Boiler for Heating and or Hot Water – FHEL Touch Screen Series from Flexiheat UK

Economic Series of Electric Central Heating Boilers 

Last but not least is our economic range of electric boilers, this range consist of two boilers only.The first is a 7.5kW electric boiler output model, that is suitable for 240V /Single phase electrical supply , and this is designated the FHELN8 , and the largest unit being the 15kW output electric boiler,which is designated the FHELN15 – this model can only be supplied with a three phase , 400 volt supply.These electric boiler for heating and / or hot water via a cylinder lack some of the features of the standard or touch screen series , in that they can use a opentherm plus controller on them ( so not optimised or compensated weather control ) , but they can use a standard room thermostat and you do have the  option to control the output temperature by 0 – 10 Volt signal. Their main advantage is the low acquisition cost or price and these units compliment our range of electric boilers, with a product that is still extremely well built and robust , but at a lower price . As with the rest of the range, they can also produce Domestic Hot Water via a indirect cylinder or calorifier. These boilers feature –

  • An inbuilt energy saving pump ErP compliant heating pump
  • Option to produce domestic hot water via an external indirect cylinder / calorifier and 3-way valve
  • Very quiet operation due to selected switching relays
  • Fluent regulation ( boiler output ) in steps of 2.5 kW for the 7.5kW electric boiler and 5kW steps for the 15kW electric boiler.
  • Minimum output of these electric central heating boilers is  2.5kW  for the 7.5kW model, and 5kW for the 15kW model
  • They have an easy to operate two-digit LED display
  • Option to control the boiler output temperature by a 0 – 10 Volt signal
  • Option to monitor the maximum current drawn to prevent overloading of the consumer board in the building/property – this system reduces the input power to the electric boiler automatically – ensuring that your main fuse does not blow.
  • Again these are electric system boilers and have an inbuilt 7 litre expansion tank
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A lower cost electric boiler – the Economic Series – from Flexiheat UK – Same quality just a lower price

Economic / Lower cost Series of Electric Boilers Technical Data

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The Economic Series of Electric Boilers – Great product at a great low price or cost – Flexiheat UK

Download the Flexiheat Brochure For Electric Boilers “FHEL” Range

Electric boilers for hot water and central heating

By using your central heating electric boiler in conjunction with a Indirect domestic hot water cylinder or tank, then you can supply plentiful amounts of Domestic Hot Water for your bathing, be it showering or filling a bath and washing up requirements.

This hot water system ensures that the electric central heating boiler not only heats your wet central electric heating system, be it radiators, under floor or a mixture of both and the hot water cylinder via the cylinders internal heating coil.

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A diagram showing how an electric central heating boiler is connected to a Domestic Hot Water Cylinder or Hot Water Tank

Using your electric central heating boiler in conjunction with solar hot water heating

An electric boiler can be used as either a “back up” or a “top up” hot water heater for a solar hot water heating system. The boiler can be used to heat up the domestic hot water which is stored in a hot water cylinder, when there is not enough solar energy to get to the desired temperature, which is normally 60 degrees centigrade for stored domestic hot water. This is achieved by using a 3-port valve and a cylinder stat.

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An Electric Boiler can be used to “top up” a solar hot water heating system

Electric Boilers – Safety Standards 

All of our Electric Central Heating Boilers / Electric Boilers have been tested in accordance with Directives 2006/95/EC (Low Voltage Directive, LVD) and 2004/108/EC (Electromagnetic Compatibility Directive, EMC) and conform to these regulations in full.

These Electric Boilers are also in compliance with the following norms and regulations:
•EN 50110-1:2003 – handling and operation with electrical installations
•EN 55014:2001 – electromagnetic compatibility -conditions for household devices, electrical devices and similar devices
•EN 60 335-1+ed.2:2003 – electrical household devices
•EN 60 335-1+ed.2 zm.A1:2005 – electrical household devices
•EN 61000-3-2 ed.3:2006 – electromagnetic compatibility(EMC) – the limit for the harmonic current emission
•EN 61000-3-3:1997 – electromagnetic compatibility (EMC)–Law on the limitation of voltage fluctuations and flickering of the low-voltage partition network

So should you be after an Electric Boiler System, or Electric System Boilers ( We also hear them be referred to an Electric Flow Boiler or even an Electric Water Boiler ) then we at Flexiheat UK are the people to talk to.

Electric boilers for sale UK & Ireland

We think that we have the best range of Electric Central Heating Boilers in the UK and Ireland for both electrically heating a wet heating system  and / or doing your domestic hot water requirements via a hot water cylinder. Should you require anymore assistance or information on our Electric Boilers / Electric Central Heating Boilers , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form