Electric Combi Boilers – 4.5 kW to 40 kW Output

 

Electric Combi Boilers or Electric Combination Boilers as they should really be referred too, are electric boilers that will do both your heating and your Domestic Hot Water requirements (often referred to as DHW). They are a increasingly popular heating and hot water solution for properties, holiday homes or households that have no access to a natural mains gas supply /gas grid or gas boiler restrictions due to flue or limited locations for installation and where oil or LPG is not practical or available, or you don’t want to burn fossil fuels for a renewable future.

You can also achieve carbon free heating when using a renewable energy tariff, such as wind generated electricity or via solar power /solar panels.

With advancements in electric boiler technology, electric combi boilers have evolved into an advanced and competitive product, they are typically easier to maintain and install unlike a gas boiler, and are extremely quiet in operation. Another benefit of electric combi boilers is that they are small and compact, so can often fit in a cupboard in the kitchen for example, or under the stairs etc and can be fitted into an existing central heating system with easy.

The other massive benefit is that they require no flue pipe system, unlike gas and oil boilers they don’t release any noxious fumes into the environment, so the risk of CO2 poisoning from a faulty flue from a gas combi boiler are eliminated, this means that you can locate your electric boiler in more locations to suit your needs, rather than having to position it to accommodate the flue system and regulations that you have to comply with gas boilers or oil. Installation costs are reduced as additional costs for fitting a flue system for the waste gases /noxious fumes are eliminated as well.

And the final point is that if your buying renewable energy from your energy supplier i.e. wind generated electricity, you can eliminate or reduce your carbon footprint with an electric boiler – something beneficial over traditional gas boilers or gas combi boilers

These energy efficient combination boilers can be used to run a traditional radiator heating system or wet underfloor heating systems just like a gas combi boilers can.

With a new electric combi boiler, Solar PV panels can also be used, and are a great option not only to reduce the use of fossil fuel but also carbon emissions, but also to save money with lower energy bills for your heating and hot water.

You will not only be making the transition to carbon-free heating with the use of a renewable energy tariff, but you will also be doing your part for a green future with an electric combi boiler,

Electric combi boilers come in a variety of outputs and the most suitable option for your property or home will depend not only on your central heating requirement but mainly on your hot water usage and the number of bathrooms you have. None of our electric combi boilers emit gases or direct pollution when operating and do not operate using fuels such as mains gas supply, LPG gas or diesel and therefore there’s no risk of leaks or explosions, or an oil tank to leak etc.

All of our electric combination boilers are highly efficient at 100%, and come with a control panel, and are fitted with the latest ErP low energy rated heating pumps.

Our electric combi boiler energy efficiency is 100%, and this is one of the biggest selling points of our electric combi boilers, as opposed to gas and oil boilers, leading to reduced running costs and lower energy bills.

Advantages of Combination Electric Boilers –

• Electric boiler prices are very competitive – cost effective, especially against an oil boiler
• Electric boiler efficiency is 100% energy efficient (better than any gas boilers)
• A gas boiler requires a flue exhaust system – An electric boiler doesn’t – making them a great option for various installation locations
• Come with an internal expansion vessel and pumps which eliminate unnecessary external plumbing
• Can be used on an underfloor heating or radiator central heating system – again just like a gas boiler
• Electric boiler installation- is a straight forward and quick task – for both a new boiler or retrofit.
• Gas Boilers need annual serving ( a legal requirement if you’re a landlord ) the best electric combi boilers like ours don’t.
• Installing electric heating systems – most electric boilers are cheaper to install than most gas boilers as a rule for a new boiler or a replacement boiler -no gas safe engineer is required.
• Greener and more environmentally friendly – eco friendly heating – these electric boilers don’t burn fuel like gas or oil, they don’t lose any energy – 100% energy efficiency (gas combi boilers are between 89-95% energy efficiency and oil boilers have 85 -93% energy efficiency)
• Can be powered by solar PV panels or battery systems, and also can be used in conjunction with traditional solar panels, as top up heaters – helping to reduce the carbon footprint and reliance on fossil fuel as well as reduce your energy costs and heating bills with electric boilers
• They produce heat in simple form – a simple immersion heater / heating element to heat the water – for the central heating systems such as underfloor heating or radiators
• Wall mounted -compact size -the boilers internal plumbing is easy to access.
• Near silent operation.
• Electric combi boilers enable you to heat water for sanitary use, only when you require it – reducing energy costs and reduced running costs with instant hot water on demand.
• If your electric you consume to generate heat is from renewable sources and not from fossil fuels or natural gas or oil boiler – then you’re helping to reduce global warming.
• No mains gas supply or bulky electric storage heaters to be installed -running costs are lower than storage heaters too – you’re not going having to predict the weather with an electric boiler
• Any proficient professional heating engineer or electric heating company can install our electric boilers, with boiler installation prices being lower than the average gas boiler
• You can significantly reduce or even eliminate your carbon footprint, if your using renewable electricity for your electric heating requirements
• The 15 kW and lower output electric boilers are an electric system boiler and include the pump and expansion vessel for the heating side

Generally electric combi boilers work just like a gas boiler version, and generate heat by electric

Electric Combination Boiler Range

We will split this up into two sections –

 

Firstly – “Traditional combi electric boilers the uses a plate heat exchanger to supply domestic hot water ” we have a 15kW electric combi boiler that is powered by a 1 Phase /240 Volt electrical supply but above 15 kW Output, these require a 3 Phase / 400 Volt power supply to operate.

New for 2025 is our 1-phase powered 15kW electric combination boiler, which will produce a good DHW flow rate and is a great option for flats or smaller houses that have one bathroom. Our 15kW electric combi boiler is the largest single-phase powered electric combi on the market and will produce 10.2 litres/minute at ΔT 30°C (temperature rise), which is enough to run a standard shower head all day long if so required.

 

This has its own dedicated manual, which can be downloaded here – 

15kW Electric Combi Boiler in sinlge phase – 240 Volt electrical supply from Flexiheat UK

For some reason we often get asked for a “24kw electric combi boiler single phase” – just to make it clear – they are not available – they are only available in a three phase electric powered unit.

The only solution in reality to getting the higher performance outputs in both your electric central heating requirements and satisfactory domestic hot water performance is to use three phase as the electrical power supply. A three-phase electrical supply isn’t fitted as standard to a normal house property in the UK, but can often be requested as the standard supply voltage especially when doing a new build, and can also be retrofitted to most existing properties. Many blocks of flats have a three-phase supply to them, as they use this to power the lifts etc.

These are true combi boilers as they produce domestic hot water on demand via a stainless steel plate heat exchanger within the electric combi boiler.

Our most popular unit is the 24kW electric combi boiler, hower we also do a 15kW, 18kW, 28kW, 32kW or the largest output is a 40kW electric combi boiler.

This range is designated the “Thermo Combi Range” and is available from 15kW to 40kW, and are wall hung units with a heating circuit temperature of 40C to 90C and a DHW temperature range of 30 to 55C.

 

 

Download the Thermo Combi -electric combi boiler manual 15kw to 40kW 3 Phase supply

 

 

Secondly – and here’s the truth – electric combi boilers under 15 kW 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 unit.

Unlike a gas combination boiler, which does an excellent job of transferring the energy from the natural gas to heat water very quickly and produce an acceptable hot water flow rate, this isn’t the case for this size electric combi boiler.

You need the power (Amps) to do this when it comes to an 12 kw electric combi boiler, and a single phase 240 Volt supply just can’t produce enough electricity in Amps required to do the hot water flow rate required.

A normal house has a 100Amp supply to it (although smaller properties,flats and older properties may have 60 Amp supply) – a 15kW electric boiler for example can use 63 Amps, turn on a kettle (13 Amps), an iron (12.5 Amps) , an electric oven (13 Amps) , a vacuum cleaner (9 Amps) , or a tumble dryer (11 Amps) or any combination of these – then you in danger of exceeding the 100 Amps and blowing your fuse, and outing your electric supply.

We have a solution for this as we use a current watcher or relief relay – which monitors the current drawn, and will reduce the consumption of the boiler ensuring that you’ll never exceed the Amps for your property – for boilers that are 15kW or under.

 

But hold on! we do have a solution for this smaller size range of electric combination boilers

In simple terms we a standard electric system boiler, in conjunction with the smallest indirect unvented hot water storage cylinder of 80 litres which is G3 compliant i.e., mains unvented hot water supply– which keeps the stored water level and thus the running costs to the lowest level – whilst providing more than adequate flow rates to satisfy even filling a bath or having 2 showers at the same time. Something that might be required for larger homes.

 

WHAT SIZE ELECTRIC COMBI BOILER DO I REQUIRE ?

As an electric combi boiler will do both the heating and the hot water – the first element of sizing the correct boiler – will be the heat loss of your home or property. The heat loss calculator for the heating requirement of the boiler.

Please see this dedicated webpage on this subject – What size electric boiler do I need?

DOMESTIC HOT WATER SIDE OF THE ELECTRIC BOILER

When the duty is under 15 kW – we supply the electric boiler and an indirect cylinder – as it the only realistic solution to ensure you have the DHW requirements satisfied.

The domestic hot water tank is made of high-quality stainless steel, an extremely hard-wearing material, and also compliant with the highest water hygiene requirements (WRAS approved). No magnesium anode is required, avoiding costly inspection and maintenance requirements, something that is required with inferior glass lined water tanks. This guarantees a long hot water tank lifespan due to stainless steel’s inherent characteristics also with simplified maintenance because no magnesium anode replacement is required.

All of our electric boilers have a domestic warm water priority system, which ensures that the DHW is always available for instant use. This ensures a great recovery time of the stainless-steel water tank, should you use all the water in one go – such as filling a bath. Thus this system is suited to provide hot water for multiple bathrooms properties.

The recovery time of 80 litre indirect cylinder in conjunction with an 15kW electric boiler, from cold to 65 Degrees C is only 21 minutes for the domestic warm water.

This domestic hot water performance ensures a plentifully supply of hot water when you require it – immediate and at the right temperature.

A few points of note –

The 80 Litre indirect domestic storage cylinder, will provide 134 litres of domestic hot water @ 40C – which is the normal bathing temperature and a standard bath uses 100 litres of water at 40 Degrees C.

So if you have a bath in your property, and want to be able to fill it quickly – then you need to look at some water storage.

When it comes to showers – a standard 5 minute shower uses approximately 40 litres of water at 40 Degrees C – so you have enough for 3 showers before the stored water needs to recover.

 

The most important thing to consider with an electric combi boiler is water temperature and flow rates.

Firstly, let’s look at some flow rates

Standard shower head has a water demand of 7 or 8 ltrs/min

Bath mixer taps – 12 litres/min

Kitchen sink taps – 4 to 6 litres/ min

Bathroom Sink taps – 4 litres/min – or cloakroom spray taps – 2 litres/min

Standard water temperatures

Here are some domestic hot water temperatures that we require in the UK –

For showering = 41 Degrees C (maximum)

For bathing (bath) water / wash basins= 43 Degrees C (maximum)

For dish washing / kitchen applications = 50 Degrees C – this temperature is required to remove grease from cooking utensils

Some of the electric combi boilers on the market are often produced in the far east, is that not only is the flow rate incredibly low but the actual water temperature they can produce is often too low as well, as they are designed for use in areas that have different incoming water temperatures to the UK and northern Europe.

Many of these electric combi boilers can only produce 6 Litres of hot water with a temperature rise of 25° C, when powered by the most popular 240 V single phase electrical supply that is used in a normal property in the UK. This poor temperature rise or uplift does not allow you to achieve your desired temperatures for showering / bathing or for dish-washing applications, with adequate flow rates

Flow rates for some of the single-phase electric combi boilers on the UK market –

10kw Electric combi boiler – 5.8 Litres / minute with a temperature rise of 25 Degrees C .

A standard shower flow is 7/8 Litres per minute!! These electric boilers just won’t work and can’t provide you with adequate DHW performance.

Let alone fill a bath in a reasonable time ! which is 12 Litres/min

 

As you can see from the blue line, which shows the average mains cold water temperature for the UK, for pretty much 7 months of the year, this temperature is only 10 Degrees C, or below.

So why does this matter? well it matters because if you have a electric combi boiler, that can only add 25 degrees C to your incoming water temperature, then your final outlet temperature at your taps / shower head is only going to be 35 Degrees C, way too low for domestic water requirements- 35 Degrees C won’t remove grease for plates etc, and a 35 Degrees C shower or bath for most people will be regarded as a cold or tepid to say the least.

Although some of these electric combi boilers claim they can produce domestic warm water up to 50 Degree C, the flow rate drops dramatically, and becomes unusable in the real world.

You would be lucky to get 2 litres a minute from a 10kW electric combi boiler, with a standard UK sink holding 15 to 18 litres of water – it would take up to 9 minutes to fill for the 10kw electric combi boiler.

These reasons are why having an electric boiler with an indirect hot water storage cylinder is the correct solution for you heating and warm water requirements when you get down to 15kW or lower of output

A DHW storage element, removes these poor flow rate problems and water temperature issues, and makes living with an electric boiler that does both heating and the hot water hassle or trouble free.

DOMESTIC HOT WATER SIDE OF THE ELECTRIC BOILER IN CONJUCTION WITH A SMALL CYLINDER

When the duty is under 15 kW – we supply the electric boiler and indirect cylinder – as it the only realistic solution to ensure you have the DHW requirements satisfied. The domestic hot water tank is made of high-quality stainless steel, an extremely hard-wearing material, and also compliant with the highest water hygiene requirements. No magnesium anode is required, avoiding costly inspection and maintenance requirements, something that is required with inferior glass lined water tanks. This guarantees a long hot water tank lifespan due to stainless steel’s inherent characteristics also with simplified maintenance because no magnesium anode replacement is required.

All of our electric boilers have a domestic warm water priority system, which ensures that the hot water is always available for instant use. This ensures a great recovery time of the stainless-steel water tank, should you use all the water in one go – such as filling a bath.

The recovery time of our 80 litre indirect hot water cylinder in conjunction with an 15kW electric boiler, from cold to 65 Degrees C is only 21 minutes for the domestic warm water.

This domestic hot water performance ensures a plentifully supply of hot water when you require it – immediate and at the right temperature.

A few points of note –

The 80 Litre indirect domestic hot water cylinder, will provide 134 litres of domestic hot water @ 40C – which is the normal bathing temperature and a standard 1 bath uses approximately 100 litres of water at 40 Degrees C

So if you have a bath in your property, and want to be able to fill it quickly – then you need to look at some water storage.

When it comes to showers – A standard 5-minute shower uses approximately 45 litres of water at 40 Degrees C

If you require a mains unvented domestic hot water system – then please look at our electric system boilers that you can use in conjunction with an indirect unvented cylinder.

Electric combi boilers installation

Installation of these electric boilers are easier than a gas combi boiler or oil for a few reason – the biggest being there is no flue pipe to install, thus the cost of this and the associated builders cost, such as making holes in brickwork or the roof for the flue are eliminated. This will often mean that fitting an electric combi boiler, is the cheapest of all combi boilers to fit when compared to oil or gas heating systems. All of our boilers can be used in conjunction with a wireless thermostat and are suitable for underfloor heating systems or a radiator central heating system

Electric combi boiler cost

Electric combination boiler prices are at the mature stage of pricing cycle, they are a well-established product and have been for many years. As a general rule the average cost is slightly higher than their alternative gas boiler at first impressions – but when you look at the extra’s such as the flue pipe etc, then they are around about the same price when you look at them as a package. When compared to an oil combi boiler, then are cheaper on a like for like kW basis, even before you add the flue pipes for the waste gases and accessories.

 

Electric Combi Boilers – Electric Combination Boilers for sale UK & Ireland

Whether you want an electric combination or electric boiler for your property, be it a house, flat, bedsit, static caravan, or for a commercial / industrial application, then we have the best range here at Flexiheat UK to satisfy you requirements with a range from 4.5kW to 40kW Output, and options of single or three phase electric powered models.

Should you require anymore assistance or information on our Electric Combination Boilers / Electric Combi Boilers for sale in the UK and Ireland, then please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.