Electric boilers: what you need to know

Similar in size and with comparable installation costs to a gas boiler, an electric boiler may appeal to those looking to reduce their carbon footprint sooner rather than later. 

But electric boilers have higher running costs than gas boilers and aren't nearly as efficient as electricity-fuelled heat pumps, which means they're not for everybody.

Read on to find out more and installation and running costs, how they stack up against alternatives and if it makes sense for you to make the switch to an electric boiler now.

Already decided you want a heat pump? Head to our guide to buying a heat pump.

The best electric boiler brands

Not enough people in our 2023 boiler survey owned electric boilers for us to score the brands on their feedback. Electric boilers are still fairly niche compared to gas boilers. 

However, you can read the results of our 2022 boiler survey of 9,722 owners and 196 boiler engineers below. We gathered results for two brands: EHC and Heatrae Sadia. Our scores are based on owner satisfaction, reliability over six years, and the opinion of Which? Trusted Traders.

Which? members can see how both brands compared against each other in our table. While one brand came out as the engineers' favourite, another was more likely to be recommended by owners. 

Are electric boilers any good?

There is no one size fits all solution, so it's worth taking some time to consider the pros and cons of different systems before parting with your money. Here, we've summarised the key pros and cons of electric boilers; we delve into what you need to know in more detail later in this article. Bear in mind that every home is different – you should always get an expert local engineer to carry out an assessment of your home before making any decisions.

Electric boiler pros

• No carbon emissions from the boiler itself – although it's only completely zero emissions if the electricity that powers it is produced from renewable sources.
• Electric boilers are nearly 100% energy-efficient – compared to a like-for-like gas boiler, you need fewer units of energy (kWh) to produce the same amount of heat. 
• Have fewer moving parts – reducing the likelihood of a fault.
• Quieter than gas boilers – mainly due to fewer moving parts. If your boiler is located in a room you spend lots of time in, an electric one may be softer on the ears.
• Can be placed almost anywhere in the home – they don't need a flue or gas pipe to run to them, so can even be placed on an internal wall.
• No risk of a carbon monoxide leak – this is a risk in faulty gas boilers if the gas is not burned completely due to a lack of oxygen and the resulting carbon monoxide escapes into your home.

Electric boiler cons

• Expensive to run – electricity is more expensive to buy per unit of energy (kWh) than gas. One kilowatt hour of electricity is currently between three to four times more expensive than one kilowatt hour of gas. 
• Less efficient than heat pumps – electric boilers are incapable of efficiencies over 100% while heat pumps can produce more units of heat than energy consumed, giving them efficiencies of 200%, 300% and even higher. This is why heat pumps, while electricity-powered, can cost less to operate than a gas boiler.
• Typically shorter warranties – most are two to three years. This is no reflection on their likelihood of breaking but, given that gas boilers can have warranties that last 10 years or more, it does mean you're more likely to have to pay for faults that do occur.
• Not suitable for larger homes – electric boilers typically have lower maximum outputs, meaning they may struggle to meet the higher heating and hot water demands of larger homes. They'll be fine for smaller homes, though. We explain why later.

What is an electric boiler?

An electric boiler works in a very similar way to a traditional gas boiler, except that it heats water by passing an electric current through a heating element rather than by burning gas – essentially operating like a big kettle (it doesn't boil the water though).

Electric boilers connect up to a central heating system to heat up the water in your radiators, and provide hot water to your taps and showers.

Types of electric boiler

Like gas boilers, electric boilers can be either combination (combi) system or heat-only (regular) boilers:

Combi boilers

Heat up water for your taps and radiators 'on demand'. They don't need external hot water storage cylinders, making them suitable for properties with less space. But as they heat the water as you need it, this uses more power than a heat-only or system electric boiler.

Heat-only boilers

Provide heat directly to your radiators, and connect up to a water tank to provide hot water.

They are best suited for larger homes with a greater hot water demand. This is because they heat and store hot water for when you need it, rather than heating it 'on demand' like a combi boiler, which may not be able to heat it fast enough to meet demand.

However, they take up more space than a combi or system boiler as they need two tanks – a hot water tank that stores the hot water ready for use (usually kept in an airing cupboard), and a cold water feed tank that's usually placed in a loft and fills up from the mains water supply.

System boilers

These are like a heat-only option, but components that are external in a heat-only boiler, such as pumps and valves, are built into the body of a system boiler. As such,  they only require a hot water tank, which saves space.  

Some manufacturers sell models with an integrated hot water cylinder, as opposed to you needing to buy a separate one. These are designed to fit completely with a standard airing cupboard, so if you have the space could be an attractive 'all-in-one' solution. 

For more pros and cons, read our guide on the different types of boiler.

Electric boiler costs

As with any heating system, there are three main costs to consider: upfront costs (for the boiler itself and for installation), running costs and maintenance costs.

Currently, electric boilers are broadly comparable with gas boilers in terms of buying the equipment and maintenance costs, but running costs are (for the time being) a different kettle of fish.

Electric boiler installation costs

Off-the-shelf prices of electric boilers are similar to that of gas boilers. You can typically get an electric combi boiler for between £1,500 to £2,000. Heat-only electric boilers can start from as little as £400; if you don't already have them you'll need to factor in the cost of any water tanks as well. 

The cost of professional installation is typically similar for gas and electric boilers too, assuming like-for-like size and type of boiler. The exact costs will depend on the complexity of the job - changing a boiler's location will add to the cost. 

There is one caveat to this assumption that costs for gas and electric boiler installations are typically similar, though. In some cases you may also need to upgrade your home's electrical infrastructure so that it can support the switch from a gas to an electric boiler. Things that can affect this include:

• The phase supply of your home and if the electric boiler is suitable for it – an electric boiler needs to suit your home's electricity supply, whether that's single or three-phase. Higher energy demands may require a change from single-phase to three-phase. 
• The size of your home's incoming supply fuse – it limits the maximum size of electric boiler you can install. We will explain in more detail later.
• The size of electric boiler (in kilowatts) – the larger size of electric boiler you need, the more likely your home will need upgrades (eg a larger incoming supply fuse). Heat-only and system electric boilers tend to have lower power demands than combi models.

If your electrics need upgrading it could dramatically drive up the installation cost of a switch from a gas to an electric boiler.

If you are considering installing an electric boiler, get your home's suitability assessed by a local expert engineer first. They can evaluate and advise on the best heating system for you.

Single-phase versus three-phase electricity supply

Electricity can be supplied to UK homes by a single-phase or three-phase supply. Buildings with higher energy needs are usually on three-phase.

You can see what 'phase' supply your home has by looking at the 'main switch' on your fuse box. If it looks like three switches combined into one then it is three-phase, if it's a single switch it's single phase. 

It may be the case that the right electric boiler for your home means your home needs to upgrade – but you should get a local expert in to assess your home's suitability for an electric boiler before committing to any switch or upgrades.

Electric boiler running costs

As it stands, electricity costs substantially more than gas per kWh. The energy unit price cap from October 1st 2023 is 6.89p per kWh of gas and 27.35p per kWh of electricity. 

While electric boilers are more efficient than gas boilers – so they use fewer units of energy to do the same job – they're not so efficient that they are able to offset the price difference. This means that electric boilers are still much more expensive to run than equivalent gas boilers. 

If you have a low heating demand, for example you live in a smaller property and/or your home is insulated well (so heat doesn't escape easily), you'll need your heating on for less time and the costs to run an electric boiler may be manageable. 

You can lower the running costs for an electric boiler by heating hot water overnight on an off-peak tariff, but these tariffs have more expensive electricity during the day. And, in any case, this is only viable if you opt for a a heat-only or system boiler with a hot water tank that can be heated before you need the water.

If you generate your own electricity, this will reduce your costs as well. 

Electric boiler maintenance costs

Electric boilers have fewer moving parts than gas boilers. For example a gas boiler includes a fan to move air through the boiler for the combustion of gas, and a gas valve to regulate the flow of gas to the burner. An electric boiler doesn't need these.

They are therefore less likely, on paper at least, to break down than their gas equivalents. 

But this doesn't mean an electric boiler will never need repairing, and if it's one of the key components (such as the heat exchanger), parts can cost upwards of £400. In addition, to help ensure they remain fault-free, manufacturers still recommend that electric boilers are serviced annually, which will be a similar price to a gas boiler service.

Factoring all this in, over a boiler's lifetime the total cost to maintain an electric boiler is likely to be similar to that of a gas boiler.

Electric boiler warranties

Electric boiler warranties are typically only for two to three years, whereas gas boiler manufacturers can offer ones that last up to 10 years or more. 

This is at least in part due to the fact that, historically, most homes have had gas boilers installed, driving up competition among manufacturers and prompting them to offer longer warranties to stand out.

If electric boilers grow in popularity among homeowners, we may see warranty lengths start to increase.  

Are you paying over the odds for your gas boiler service and repairs? Read our expert guide on boiler repair costs and getting the best boiler service.  

What size of electric boiler do you need?

The size of an electric boiler is measured by its power output in kilowatts (kW). The higher the kW output, the larger the home it can heat.

Electric boilers typically have smaller kW outputs than gas or oil boilers. An average electric boiler size is around 15kW or less, while you can get gas combi boilers anywhere from 20kW to 40kW or more.    

This means electric boilers are well-sized for smaller homes, but may struggle to meet the heating demands of larger properties, especially if you don't have the space for a heat-only or system boiler, and would have to go for a combi electric boiler. 

In addition, the overall size of your home, the number of radiators, how well insulated it is and your hot water needs (whether you run multiple hot water taps at the same time, for example) will all also affect the size of boiler you need.

It's best to get a qualified heating engineer to carry out an assessment of your home to determine the best size boiler for it. 

If you need an engineer, make sure it's a Which? Trusted Trader. They have all been vetted by our trading standards professionals – not just anyone can become endorsed. Use our search tool, below, to find a local trader in your area.

Why do electric boilers have lower maximum power outputs?

The maximum power output of electric boilers is limited by the typical capacity of a home's incoming supply cable and the size of the supply fuse (also known as the main electrical fuse). An incoming supply fuse exists to prevent an excessive current damaging your home's cables or electrical devices. 

If you have too many electrical devices running at once it can risk blowing the supply fuse. Day-to-day this isn't an issue, as the pull of most household devices won't be enough to blow this fuse, even when several are in use at once. But electric boilers are 'current-hungry', and the larger the electric boiler the more current it will use.

You don't want a situation where your electric boiler is too large for your home's electrical capacity. This is limited by the size of your home's incoming supply cable and supply fuse. As a rule of thumb, installers recommend you limit the size of an electric boiler to less than 50% of the supply fuse size.

UK homes can have a variety of supply fuse sizes, but let's say yours is 100 amps. This means your home's electrical equipment, including your boiler, can draw up to 100 amps in total at any given time.

A 10kW boiler, for example, will typically draw 45 amps when running, nearly half of the total capacity of a 100 amp fuse. However, a 15kW electric boiler would draw around 65 amps when running, well above the 50% limit.

Working out the size of electric boiler suitable for your home can be tricky, so we recommend getting a qualified electrician to carry out an assessment. 

Are electric boilers better for the environment?

According to the government's 2021 Heat and Building's Strategy, about 17% of UK carbon emissions come from heating our homes.

When running, electric boilers don’t produce any emissions, whereas gas and oil boilers do. So if you are looking at emissions solely from the home, then electric boilers are much better than gas boilers.

As is often the case, however, it's not quite that simple. Production of the electricity itself has a carbon footprint, and that will remain the case until all the UK's electricity supply comes from renewable sources.

So it's currently impossible for your electric boiler to be completely emission-free, although electricity will get greener as we move increasingly towards renewable electricity sources. Compare this to gas, which is a fossil fuel with a high carbon footprint, it's fair to say that, overall, electric boilers are long-term better for the environment.

Electric boilers vs gas boilers

The clearest benefit of electric boilers over their gas (and oil) counterparts is that they do not release any carbon emissions at the home, helping you reduce your personal carbon footprint.

They also don’t need a flue so can be installed on internal walls, giving you more options on where to locate the boiler in the house. The lack of a flue also makes it easier to install and service electric boilers in high-rise buildings - so long as the building has the suitable electrical infrastructure. 

However it is still much cheaper to heat your home with a gas boiler compared to an electric boiler. This could change in the future but is the case now.

Electric boilers may also struggle to heat larger homes with greater hot water demands due to the limited sizes available, so may not be a viable option for homes with multiple bathrooms or lots of bedrooms. 

Additionally, if you are switching from a gas to an electric boiler, your home's electrical system may need upgrading, which could dramatically increase the installation costs. 

If you prefer to stick with gas for now, our guide on which gas boilers are energy efficient can help you lower your home's carbon footprint.

Alternatives to electric or gas boilers

A boiler – whether gas or electric - is just one way of heating your home. The most common alternative available today is heat pumps, but we expect to see other solutions hit the market over the next few years.

Electric boilers vs heat pumps

Heat pumps essentially work like a refrigerator in reverse. They take heat (from the air or ground depending on the type of heat pump) and boost it to a higher temperature using a compressor. They come in sizes that are able to heat larger homes, but need the space to house external unit(s) and for your home to be well insulated to prevent running costs sky-rocketing. 

Heat pumps are more energy-efficient than electric boilers. This means that, when set up in a suitable home, heat pumps will be cheaper to run than electric boilers. While both heat pumps and electric boilers are currently more expensive to run than gas, if electricity and gas prices balance out in the future, heat pumps could be the most economical option. 

However, electric boilers are currently cheaper to install than heat pumps, meaning that an electric boiler may still work out cheaper over its lifetime than an air source heat pump.

But you can access generous grants from the government to make installing an air source or ground source heat pump more manageable. In England and Wales this ranges from £5,000 - £6,000 and in Scotland this goes up to £7,500. 

Read our full guides to air source heat pumps and ground source heat pumps for all the details on these systems and whether they could be a good choice for your home. 

Other low-carbon heating solutions

Low-carbon options available today are limited, but as we move towards net zero more solutions, and therefore more choice, could appear. Here are a few to consider:

• Storage heaters – use electricity to heat up special heat-retaining bricks (usually over night) and then release the heat during the day. Modern storage heaters can now come with thermostats and timers. 
• Immersion heaters – electric water heaters that sits inside hot water cylinders. They are connected to their own power supply via a cable, and can be used as a primary water heater, or as a back-up water heater for combi boilers.
• Infrared panels – these provide heat by radiation. They use less electricity to provide the same amount of heat compared to electric boilers and storage heaters, but to feel the benefits there needs to be no obstacles between the heater and you (just like how you feel warm in the sun, but cooler in shade).
• Microwave boilers – made by HeatWayV, these heat your water in the same way a microwave heats up the water in your food, but use a feedback system to tune the amount of power used, so there is almost no energy waste. The company is starting in-home trials this year.

See our full guide to storage heaters and immersion heaters for more information.

Who should consider an electric boiler?

The high running costs of electric boilers are likely to put many people off making the switch for the time being, but there are some circumstances in which an electric boiler could be the right choice in the short term. 

While you should always seek the advice of a reliable and expert local engineer when choosing the best heating system for your home, an electric boiler is more likely to be a viable option if: 

• Your home is off the gas grid and you’re looking for a low-carbon heating system, perhaps as an alternative to an existing oil boiler
• You live in a high-rise building where an electric boiler would be easier to maintain and service than a gas boiler
• You want to make a more environmentally-friendly heating choice, but your home isn't suitable for a heat pump (for example, you don't have the outdoor space).

Want a gas or oil boiler from a reliable brand? Head to our best boilers guide.