Electric Boilers / Electric Central Heating Boilers – 6kW to 27kW

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. the 6kW and 9kW units are available in 240 volt , Single Phase , after 9kW 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 – 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 possibility of exceeding your supply and tripping out fuses etc.

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 Range 

We do two different models , firstly the “Classic”  Range , which is an electric central heating only boiler which are also referred to as a system boiler. These electric central heating boilers will heat up the water that is then fed to your radiators or underfloor heating system only, via a pump that is fitted internally within the electric boiler unit . These units also have an 8 litre expansion vessel fitted internally, so usually no other expansion vessels are required for the central heating system.The compact range is available in 6kW,9kW,12kW,18kW,24kW and a 27kW Output models.

The “EPlus” Range is the more sophisticated model that allows the electric central heating boiler to also produce domestic hot water via a cylinder, and to fully control the production of domestic hot water, so you can enjoy the benefits of reduced electrical rates/prices such as economy 7 etc,as well being able to have more heating control ,and a winter / summer mode. These electric central heating boilers also have an inbuilt circulation pump and expansion vessel , just like the compact unit.This Eplus range is available in 6kW,9kW,12kW,18kW, and a 24kW Output models

Both ranges are self contained electric boilers – the only thing you need to add to complete the system is a room stat (which must be Volt Free Contact) and an external filling loop – both of which you can purchase from us.

  • Standard equipment built into our electric boilers includes: body of the boiler with electric heaters, circulation pump, expansion vessel, safety elements (safety valve, safety thermostat and a pressure switch), filling/draining cock and modular digital control.
  • The modular digital control assures optimal operation of the electric heater in a way that optimizes electric energy consumption with the rated thermal output of the electric boiler.

Below is a quick reference chart showing the differences between the two units –

Classic Modele Plus Model
Heating Power -Adjustable in stepsMax 3 Steps i.e. The 9kw unit , will do 3,6 or 9kWMax 9 Steps e.g The 24kw unit has 9 x 2.7kW steps
Time Clock ControlYesYes
Circuit BreakersYesYes
Connection Size – Flow & Return3/4″3/4″
Level of ProtectionIP40IP40
Processor UnitYesYes
Display2 NumbersLCD Blue Back Light
Winter/Summer ModeNoYes
Hot Water PreperationNoYes
PumpWilo Yonus PARA MSL/MSL 12-5/3 oemWilo Yonus PARA MSL/MSL 12-5/3 oem
Expansion VesselYesYes
Safety ValveYesYes
Drian ValveYesYes
Timer For Hot Water ModeNoYes
Digital Pressure SensorYesYes
Alarms and Errors of Pressure and TempYesYes
Modular Heaters Switch on/offYesYes
External Cylinder SensorNoYes
Single Phase ConnectionYes  –   6kW & 9kW Model- 3 Phase aboveYes  –  6kW & 9kW Model- 3 Phase above

The ‘Classic’ Electric Central Heating Boiler Information

To summarize, the ‘Classic’ range of electric boilers are a heat only or system boiler, and cannot be used to heat or control the domestic hot water cylinder, it just heats the radiators or underfloor heating system and is available in outputs from 6kW to 27kW , the two smaller sizes i.e. the 6kW and 9kW are available in 240Volt / Single Phase, the rest of the range is only available in 415V / Three Phase.These Electric Central Heating Boilers work up to maximum temperature of 80°C and minimum pressure of 0.7 bar to maximum pressure of 2.6 bar.

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Electric Boilers – Electric Central Heating Boilers

Classic Electric System Boiler
Technical Table for Compact Range of Electric Central Heating Boilers

Technical Table for Compact Range of Electric Central Heating Boilers

The Eplus Electric Boiler Information

To summarize, the Eplus range of electric boilers, are an electric central heating boiler, which heats radiators or an underfloor heating system and also can also be used to heat and control the domestic hot water cylinder. It is available in outputs from 6kW to 24kW, the two smaller sizes i.e. the 6kW and 9kW are available in 240Volt / Single Phase, the rest of the range is only available in 415V / Three Phase. The boiler will produce water up to a maximum temperature of 80 °C, a minimum pressure of 0.8 bar and a maximum pressure of 2.2 bar. It has a microprocessor control unit built into the unit, and as standard comes with a cylinder stat.

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Electric Boiler – Electric Central Heating Boiler

Eplus Electric Boiler Technical Table for Eplus Range of Electric Boilers

Electric Boilers – Safety

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

Download Classic Boiler Manual

Download ePlus Boiler Manual

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

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