12kw Electric Combi Boiler

12kW Electric combi boiler – What are your options?

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12kw electric combi boiler option – Flexiheat UK

An 12kW electric combi boiler can be the perfect solution to your heating and hot water demands for a small house or flat. An electric combination boiler does away with the need for stored hot water but with this comes some things you need to be aware of to decide if a combination electric boiler is right for your application.

Here Flexiheat UK, we have a couple of options for your 12kw electric combi boiler requirements. We do a range of 12kw electric combi boilers, that can either be run off a 240 Volt / Single Phase electric supply (the most common household electrical supply voltage for the UK and Ireland)

The term “combi” is just an abbreviation for the word “combination” and when used in the context of a 12kw electric combi boiler, this means that the electric boiler will not only do the central heating requirements, but also produce domestic hot water, for your hot water taps within your property or flat. They’re ideal for properties with gas boiler restrictions, such as flueing issues, or no access to the mains gas supply. They are the perfect solution /cost effective alternative for replacing existing gas boiler, electric storage heating or solid fuel wet central heating systems with electric boilers and reduce your carbon footprint.

Ok that’s the good news, but here’s reality

Electric combi boilers under 15 kW on the market don’t work – in the real world!

Why? you just can’t get useful hot water performance out of a single phase 240 volt powered electric combi boiler unit.

Unlike a gas combi boiler, which does an outstanding job of quickly transferring energy from natural gas to heat water and producing an appropriate hot water flow rate, this is not the case with an electric boiler of this size.

When it comes to an electric boiler, you need the power (Amps) to do this, and a single phase 240 Volt supply can’t generate the Amps necessary to accomplish the requisite hot water flow rate even for smaller properties – if you do have 3 Phase then look at this webpage – Electric Combi Boilers for units that start at 15kW and above.

What’s the solution then?

Essentially, we use a standard electric boiler with the minimum sized indirect hot water storage cylinder, which is an mains-unvented hot water type – it is only 80 litres in volume, to make up a “12kw electric combi boiler”.

This results in the lowest water storage level, but enough hot water supply to cope with your properties needs i.e., it not only provides sufficient water volume, but also at the right temperatures as you require 50C to be able to wash the grease of dishes / kitchen utensils. Whilst reducing your energy costs to the minimum for your domestic hot water heating system.

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15kW and below electric combi boilers solution from Flexiheat UK

12kW Electric Combination Boiler Efficiency & Benefits

None of our 12kW electric combination boilers options emit gases or direct pollution when operating as they are not using fuels such as natural gas, LPG gas or Oil and therefore there is no risk of leaks or explosions. All of our electric combination boilers are highly efficient at above 99%, and come with a control panel, and are fitted with the latest ErP low energy rated heating pumps and come with a system expansion vessel. Our electric combi boiler benefits and key features are –  

  • A fully qualified ErP compliant 12 kW Electric Combination Boiler combined with a
  • 80 litres of Domestic Hot Water Storage
  • Heating and hot water superior performance
  • They can be used with a wet underfloor heating system
  • They can be used on a a traditional wet central heating system with radiators
  • They can be used in conjunction with solar heating systems
  • Come with an energy efficient ErP compliant heating pump
  • Fully modulating power / output regulation
  • Full controller over your required operating temperatures
  • Inbuilt control panel / programmer or can be connected to a wi fi wireless thermostat or traditional room thermostat
  • Can be controlled by an “OpenTherm” compatible controller, such as your Hive or Nest type controllers -meaning you can control the “electric combi boiler” from an app on your phone or tablet.
  • A frost / freezing protection system – If the temperature of the water inside the 12kw electric combi boiler is under 5°C, the pump and heating elements will operate to bringing the water temperature up to 35 Degrees Centigrade, ensuring that the boiler is protected against freezing and any potential damage.

They can be installed by any competent electric heating company or a plumber in conjunction with a electrician. 

Domestic Hot Water Performance

One of the most important factors in relation to electric combination boilers is their Domestic Hot Water ( sometimes referred to as DHW) performance. With 12 kW of heating power dedicated to heating the domestic water when required, which ensure a great recovery time of the stainless-steel water tank, which is a very compact unit ,should you use all the water in one go – such as filling a bath.

The recovery time of 80 litre tank, (which can be mounted directly underneath the wall hung electric boiler or in a sperate location to suit site requirements ) from 10 Degrees C to 60 Degrees C is only 29 minutes – and only 15 minutes from 35 Degrees C to 60 Degrees C. The temperature of the domestic hot water can be controlled between 35 to 65 degrees centigrade for anti legionella requirements, and comes as standard with a 3kW immersion heater, for use as a back up heater.

Kitchen taps – flow rates of between 4 to 6 litres per 
minute. These days water efficient taps and showers should have the following flow rates –

Showers – flow rates of approximately 8 litres per minute for a standard shower head.

So with 80 litres of storage of domestic hot water , a standard shower uses 65.1 litres of water blended down to 43 Degrees C and lasts for 8.2 minutes at average flow rate of 8 litres . The 80 litre stainless steel DHW tank will provide 83.3 Litres of water , when stored at 60C and blended down to 43C, which is the highest safe showering/bathing water temperature. Ensuring you have a nice warm shower, at a good water pressure, up to 7 Bar if required.


Electrical Consumption Details  – including fuse & cable requirements :-

These 12kW electric combi boilers can be wired up either with a single phase 240 volt or a Three phase 400 volt electrical supply, 


The following information is relevant when this 12kW electric combination boiler is wired up to a 240 Volt , Single Phase electrical supply –


12kW Electric combi boilers for sale UK & Ireland

The full brochure for this 12kw electric combi boiler and the rest of our range as we also do three phase electric versions that go up to 21 kW of heating output, please download our brochure here – 


Should you require anymore assistance, more information or a price on our 12kW Electric Combi Boiler / 12kW Electric Combination Boilers , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.