The UK government is working towards its goal of banning gas boilers in new builds from 2025 onwards, which means a lot of people will soon be looking for alternative ways to heat their homes (check out the price of a new boiler).
Amongst other contenders, electric boilers could become a popular choice in the coming years. Unlike heat pumps and infrared panels, electric boilers work pretty much in the same way as regular gas ones – they’re just powered differently.
Considering ditching your old boiler for an electric one? Read on to find out everything you need to know about this heating system. Alternatively, if you’re ready to take the plunge, fill in this form to find out how much a new electric boiler will cost you.
Electric boilers are pretty self explanatory – they work in a similar way to traditional gas boilers, but instead of running on gas, they use electricity to heat water. This means they produce fewer carbon emissions than gas and oil boilers, especially if they’re paired with solar panels.
Generally, electric boilers have an efficiency rating of 99–100%, compared to 92–93% in gas boilers.
The boiler itself can come in a variety of shapes and styles, making it suitable for a variety of properties. It’s particularly useful for homes that have limited access to mains gas supply, such as listed buildings.
Read about new boiler costs here for all you'll need on what you might spend on one.
Similar to a traditional gas combi boiler, electric boilers source cold water from the mains water supply. The boiler then heats this water by using electricity from the mains electricity supply, which powers the heating element within the boiler, each time you need hot water for your central heating or hot taps.
As the cold water passes over the metal heating element, heat is transferred, resulting in hot water that can either be used around the house or stored for later use.
Bear in mind that the exact process varies, depending on the type of electric boiler you go for.
An electric combi boiler combines water heating and central heating within one small unit, meaning homeowners don’t need to have a bulky water storage tank – ideal for smaller properties.
Whenever you turn the hot water tap or pop the heating on, cold water is sourced from the mains, goes through the combi, and gets warmed by the heat exchanger.
This type of electric boiler heats up water when you need it, which is great for both the environment and your wallet, but it means it might take a few seconds to warm up.
Unlike combi boilers, electric system boilers have a water tank to star water, like a traditional boiler. A coil inside the cylinder of the electric system boiler heats the water, and transfers it to the taps and central heating.
By using a separate cylinder for storing water, system boilers are able to provide a constant supply of hot water throughout the home. This is the primary reason why system boilers are commonly found in larger homes with greater demands for heating and hot water.
This type of electric boiler utilises electricity during off-peak hours, which is much more affordable for users. It does this by storing heat in a dry material, such as bricks, which can then be released at times when electricity prices are higher, saving homeowners money on bills.
Although they’re similar to regular storage boilers, dry core storage boilers are much more versatile, since the heat is released into the water only when it’s needed.
Heat-only boilers, also known as conventional boilers, work by heating water and distributing it throughout a home using motorised valves, pumps, and tanks.
A cold water tank – usually stored in the loft – takes water from the mains and feeds it into a hot water cylinder. The boiler then heats the hot water cylinder, and supplies it to taps and central heating.
These boilers are best suited for larger homes with greater hot water demand because they store hot water for when you need it, rather than heating it ‘on demand'.
This heating system is very similar to a system boiler, but will a few minor tweaks. According to Valliant, the main difference is that heat-only boilers maintain pressure using a feed and expansion tank, whereas system boilers use a pressurised heating circuit topped up by mains water.
The size of the electric boiler you’ll need will depend on a range of factors, including the size of your property, the number of people living in the building, and how frequently you need hot water.
Electric boiler size is based on the energy output (kilowatts) rather than physical size – the higher the kilowatt (kW) rating, the more taps and radiators it can supply.
According to boiler manufacturer Viessmann, as a basic rule, you should add 1.5 kW for every radiator in your home. So if you have six radiators, you’ll need a 9 kW electric boiler. However, this rule will vary depending on how high your ceilings are, whether you have single or double glazing, and how effective your insulation is.
Electric boilers tend to have a much lower kW power output than gas or oil boilers. However, the exact amount of electricity your boiler gets through will depend on the type of boiler and how much you use it.
For context, the average three-bedroom house will get through 12,366 kWh per year powering an electric combi boiler.
Electric boiler costs vary, depending on the model and manufacturer. On average, you can expect to pay roughly £2,325 for an electric boiler, which includes installation costs.
It’s also important to bear in mind that electric boilers are much more expensive to run than gas and oil boilers. This is because electricity is 3-4 times more expensive than gas per kilowatt hour (kWh).
In fact, we worked out that the cheapest way to heat your home is with a gas boiler, which will cost you £12,553 over 10 years (for a three-bedroom house). An electric boiler, on the other hand, will cost £20,522 over a decade – about £7,969 more than a gas boiler.
Want to pear your electric boiler with solar panels? You can learn more about this in our helpful guide: Can Solar Panels Heat A House In The UK?
There aren’t any government grants that are targeted specifically at electric boilers, but some people might be able to upgrade their current boiler to an electric one through the ECO4 scheme.
However, not everyone will be able to apply for this grant, since it’s aimed at low-income households in the UK.
You could be eligible for the ECO scheme if you receive any of the following benefits:
The new phase of the grant also supports inefficient social housing and private rented housing (if the landlord permits it).
Since immersion heaters and electric boilers both run on electricity, replacing one with the other should be a relatively quick job. Although, this will depend on how easy it is to access the unit, and whether there are any installation issues.
Generally, replacing an immersion heater with an electric boiler can take anywhere between two hours up to half a day. However, bear in mind that you might need additional work carried out by an electrician if there’s an electrical fault affecting the unit.
Electric boilers have their fair share of pros and cons. Although they’re better for the environment than gas boilers and have a higher efficiency rating, they’re also much more expensive to run – costing more than £7,969 more to run than gas boilers over ten years, to be exact.
However, as we get close to the government banning gas boilers, electric boilers will become more appealing to people around the UK.
If you think your home would be suitable for an electric boiler, you’ll need to find out how much it’ll cost you before taking the plunge. Luckily we can speed up that process.
You can receive bespoke electric boiler quotes by popping a few details in this short form. Once we’ve received your details, we’ll pass them on to our suppliers, who’ll get in touch with free quotes.
Electric boilers are often labelled as being 99-100% efficient, yet the very same unit will also receive a D-rating for efficiency. This is in comparison to gas boilers that tend to achieve efficiencies in the region of 92% yet achieve an A-rating.
So, how efficient are electric boilers and why aren't they A-rated? The answer is because the majority of electricity generation in the UK is done with fossil fuels, a process that emits twice as much carbon as natural gas.
The efficiency of all boilers, no matter the fuel type, is shown as a percentage and as an ErP rating. The percentage gives you an idea of how much energy is wasted as the boiler operates, while ErP ratings were introduced by the European Union (EU) to label boilers with a rating from A+++ (highest level of efficiency) down to a G (lowest efficiency rating).
Comparing the efficiency of electric, gas and oil boilers side-by-side can be challenging because despite being 99-100% efficient, electric boilers tend to have an ErP rating of D. On the other hand, all condensing gas and oil boilers must reach a minimum efficiency level of 92%, yet this is enough to award them an ErP A-rating.
Manufacturer Boiler model Fuel type Output Energy efficiency ErP rating Ferroli LEB TS Electric 12 kW 99.5% D Worcester Bosch Greenstar 9i Gas 9 kW 93% A Firebird Envirogreen? Kitchen Oil 18 kW 93% AThe reason electric boilers, in this case the Ferroli LEB TS, has such a high efficiency rating is because little to no energy is lost during operation. Meanwhile, 7% of the fuel being used by these gas and oil boilers is being wasted, which means that for every £1 spent on heating the home, 7p is lost. Gas and oil boilers can't match electric boilers in terms of energy efficiency, as they very rarely achieve an efficiency above 93%.
So, in terms of energy efficiency, the electric boiler is the outright leader but the ErP rating is much lower – which is why comparing electric boilers with gas and oil units can get confusing. The reason for this comes down to how electricity is generated and how much it costs to run.
Looking to find out more about gas boiler efficiency? Have a read through Boiler Efficiency Explained.
In the UK, electricity is generated in a number of ways to ensure that there's a constant supply, including:
The vast majority of UK electricity generation comes from fossil fuels, which not only has a negative impact on the environment but is becoming increasingly expensive. This goes some way to explaining the low efficiency ratings of electric boilers.
All boilers have an ErP (Energy related Products Directive) rating that gives consumers a clear understanding of how efficiently a boiler will run, from A down to G.
When looking at gas boilers, you'll see they're pretty much all A-rated, while electric boilers tend to be D-rated and there are a couple of reasons for this:
The emissions of natural gas production, before being delivered to the home, is 0.216kg of CO2 per kilowatt-hour (kWh). Meanwhile, emissions from electricity generation is 0.519 kg of CO2 per kWh. That's more than double the emissions from natural gas and, as a result, electricity is considered more carbon intensive than natural gas.
Now for the technical part.
As electricity carries the weight of being a carbon intensive fuel, units of electricity are divided by a 'fuel factor', reducing the efficiency. The fuel factor is worked out by calculating the square root of the ratio of the carbon emission for the fuel (electricity in this case) to the emissions factor for gas. This gives electricity a fuel factor of 1.55, higher than gas, LPG and oil. You can see the fuel factor mathematics in the table below.
Carbon Emissions (kgCO2per kWh) Multiple of Gas Emissions Fuel Factor Natural Gas 0.216 1.00 Electricity 0.519 1.55 LPG 0.241 1.06 Oil 0.298 1.17The only way for this fuel factor to drop, and the ErP rating to increase, is for more energy suppliers to generate electricity with renewable technology. Which could happen by as soon as 2025 with the National Grid commenting: "We believe that by 2025 we will be able to fully operate Great Britain's electricity system with zero carbon."
It’s true that electricity generation is becoming less reliant on fossil fuels but while they’re still used, electric boilers will likely still be D-rated for efficiency. Even if all electricity generation became 100% renewable, it would probably take a fair amount of time for relevant regulators and decision-makers to give electric boilers an improved efficiency rating.
So, while an electric boiler can heat water with little to no heat loss, giving the unit a 99-100% efficiency, the fuel factor sees the ErP rating appear low as the generation back at the power station produces high volumes of carbon. As well as this, electricity is expensive to run, which also drives the ErP rating down.
You'll also need to look out for the efficiency rating of the hot water cylinder. The cylinder stores hot water, ready to be used when needed around the home. How well insulated the cylinder is will determine how much heat escapes and whether any excess energy will be needed to heat the water back up again. This higher the efficiency rating, the better the hot water cylinder is at preventing heat from escaping.
Get boiler quotes to supply and fit a new boiler now.
Even if you're with a renewable energy supplier, who produces electricity using solar or wind, your electric boiler will still be considered D-rated because this 'fuel factor' is given to all electricity, no matter how it's generated.
In better news for electricity, the 'fuel factor' is expected to drop as more and more energy suppliers switch to a renewable form of energy generation.
As electricity is expensive, running an electric boiler can increase your energy bills, which is why it's worth looking for a cheaper tariff – the best option is an Economy 7 or Economy 10 tariff.
These tariffs offer cheaper rates for electricity during the night, normally from midnight to 7am or 10am, depending on the tariff and energy supplier.
Having a tariff that offers lower rates through the night gives you the opportunity for your electric boiler to heat water at night and keep it stored in a hot water cylinder until you need it during the day.
It's also possible to install an electric boiler as part of a solar PV system to power the boiler with free renewable solar energy and reduce the reliance on your energy supplier. Fit a solar battery and you'll have a supply of renewable energy when the sun goes down too.
Compatible water cylinders can also be fitted with solar thermal, which will heat the water so that the electric boiler doesn't have to, using less electricity as a result. It's worth remembering that solar thermal will only work during the day, so you might want to compliment it with an Economy 7 or 10 tariff for hot water during the night, if needed.
There might be some confusion around the efficiency ratings awarded to electric boilers but there are some crystal clear benefits to having one installed:
Read our guide to the Best Electric Boilers to find the right model for your home.
If you're looking to replace your gas boiler with an electric boiler, you'll need a Gas Safe registered engineer to remove the gas boiler and then fit the electric boiler. Once fitted, an electrician will be needed to complete the wiring.
The price of an electric boiler installation will vary from installer to installer, which makes comparing quotes from multiple heating engineers essential to find the most competitive price. To make getting several quotes easier, complete our simple online form and you'll get free boiler quotes from up to 3 fully-qualified electric boiler installers in your local area.
Get boiler quotes to supply and fit a new boiler now.
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.
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