Electric Boilers Explained

An electric boiler does the same job as a gas boiler, heating water that then circulates through radiators or underfloor heating pipes, but it uses electricity as its fuel rather than burning gas¹. Most electric boilers sold are combi models, sending hot water both to the heating circuit and to the hot water supply, and they can also be connected to a water tank for stored hot water². Because nothing is burned, there is no flue and no gas pipe, which opens up siting options a gas boiler simply does not have.

The trade-off is running cost. Electric boilers are highly efficient at the appliance, with most units offering at least 99% efficiency³, but electricity is an expensive fuel to buy, and annual running costs for an average home have been put at £2,690 on an Economy 7 tariff for a flat or small home, and around £3,220 on a single-rate tariff⁴. Installation costs £3,000 to £6,000⁴, and the technology is generally best suited to smaller properties and homes off the gas grid⁵.

How an electric boiler heats your home

An electric boiler is a "wet" system appliance: it uses electricity to heat water, and that water is then sent through radiators or underfloor heating pipes, exactly as it would be from a gas or oil boiler¹. The radiators, the pipework and the controls are the same as those in any conventional central heating system, which is why an electric boiler is often described as a like-for-like replacement for a gas boiler in homes where gas is not available or not wanted. If you want to compare the system types, see combi boilers, system boilers and regular boilers.

Most electric boilers on the market are combi models, meaning they channel hot water through the radiators or underfloor heating and also heat the home's hot water supply². Where stored hot water is wanted, an electric boiler can be connected to a water tank, and systems usually include a large hot water tank to store the heat². That stored hot water matters for two reasons: it lets the boiler heat water when electricity is cheaper, and it provides a buffer of hot water for baths and showers. Homes with a cylinder can learn more in hot water cylinders.

The other defining feature is what is absent. There is no combustion, no flue, no gas pipe and no oil tank, so the appliance itself is compact and quiet, and the hazards associated with burning fuel in the home are removed at the appliance. The dependence that remains is on the electricity supply: an electric boiler is only as clean and only as cheap as the electricity feeding it, which is why the sections on efficiency, running costs and tariffs below carry more weight for this technology than for any other boiler type.

How efficient are electric boilers? Up to 99% at the point of use

Most electric combi boilers offer at least 99% efficiency³, and makers describe the thermal efficiency as almost 100%, because generating heat from electricity does not involve the flue losses that come from burning a fuel². Every unit of electricity that enters the boiler is converted into heat in the water, with no chimney for heat to escape up.

That figure is true, and it is also not the whole story. Efficiency at the appliance is not the same as value at the meter, because electricity is bought at a much higher price per unit than gas. Energy Saving Trust puts it plainly: even though electric heating is more efficient than using a boiler, the higher cost of electricity more than offsets that advantage¹. A gas boiler may convert 90-odd per cent of its fuel into heat while an electric boiler converts nearly all of it, and the electric boiler can still cost far more to run per unit of heat delivered.

For a household thinking about energy independence, this is the central fact about electric boilers. The appliance itself wastes almost nothing, but it ties the home's heating bill to the price of grid electricity, which is the most expensive heating fuel on the market and one the householder cannot shop around for in physical terms, only in tariff terms. The efficiency story only becomes favourable when the electricity is cheap, as with off-peak tariffs, or self-generated, as with solar panels. Both routes are covered later in this page.

Running costs: £2,690 to £3,220 a year

Two independent figures for annual running costs exist, and they differ because they describe different homes on different tariffs. The Centre for Sustainable Energy puts the annual space heating cost of an electric boiler on an Economy 7 tariff at £2,690 for an average flat or small home, and puts flow boilers at around £3,220 a year on a single-rate tariff for an average home⁴. The first figure benefits from cheaper overnight electricity; the second pays the full single rate for every unit. Both were published in June 2026.

For comparison, modelling for gas boilers installed in 2030 puts the median annualised total cost at between £710 and £1,960 depending on the home⁷. The gap between those numbers and the electric figures is the price of electricity relative to gas, not a difference in appliance efficiency. Part of that gap is policy rather than physics: a typical household with a gas boiler pays £229 per year in levies across heating and non-heating uses, equivalent to 10% of all energy bills, costs that are recovered through electricity bills rather than gas bills⁶. Proposals to rebalance these levies are part of the wider debate about making electric heating competitive.

What drives the annual figure in practice is the size of the home, the insulation, the tariff and how much hot water the household uses. A small, well-insulated flat on an off-peak tariff sits at the cheaper end; a larger home on a single-rate tariff sits well above it. The detail behind these numbers, and how electricity compares with gas, oil and other fuels, is covered in electric heating running costs and heating running costs by fuel.

What an electric boiler costs to buy and install

Electric boilers cost £3,000 to £6,000 to install, according to the Centre for Sustainable Energy, as of June 2026⁴. That fitted figure covers the appliance and the installation work, and it sits within the range of what other boiler types cost, though the breakdown differs because there is no flue to fit and no gas connection to make, but there may be electrical work to do instead.

Looking at appliance prices alone, statistics collected in January 2024 put wall-mounted electric boilers with a cylinder, in the 3 to 15kW range, at £1,750 to £2,000, an average of £1,875, and electric boilers with an in-built cylinder, at 12kW, at £1,500 to £2,500, an average of £2,000³. For context on the wider market, a new boiler of any type costs around £1,500 according to Checkatrade⁸, and interim boilers, fitted as a stopgap when heating has failed, come in at around £1,500 upfront, generating a monthly cost of about £12.50⁹. Biomass boilers sit far higher, at £5,000 to £10,000 for the boiler alone⁸.

Appliance prices from UK boiler statistics, January 2024³.

Two cautions apply to the headline install figure. First, changing fuel to an electric boiler is likely to require rewiring and possibly a new supply fuse, work that adds to the cost of the job¹⁰. Second, VAT is charged at the full rate: energy-efficient boilers do not qualify for the reduced VAT treatment available for some energy-saving products, so 20% applies¹¹. A full cost comparison across fuel types is in new boiler cost.

Which homes suit an electric boiler: flats, small dwellings and those off the gas grid

Electric boilers suit homes off the gas grid, and because there is no flue, they allow more flexibility over installation than a flued appliance does⁵. They are generally associated with smaller properties¹², and makers describe the electric boiler as particularly suited to boosting heating and hot water supply in small urban homes². That combination, no gas connection available and modest heat demand, is where the technology fits.

The reason size matters so much is cost rather than capability. Using an electric boiler to provide heating and hot water for a larger home can quickly become very expensive, because of the high price of electricity². Sizing guidance illustrates the scale: a 24 to 30kW boiler is suitable for any home with up to three bedrooms, whereas larger houses require a boiler of 35kW or more³. Electric boilers in the common 3 to 15kW range³ therefore line up with flats, terraces and small semis rather than large detached houses. More on choosing output is in boiler sizing.

For off-grid households, the realistic alternatives are oil, LPG, biomass or a heat pump, each of which brings its own storage, delivery or infrastructure requirements, covered in off-grid home heating. An electric boiler removes the fuel delivery, the tank and the combustion, and replaces them with a single dependence on the electricity supply. Whether that is a better position depends on the home: a small, well-insulated property with low heat demand loses little by heating with electricity, while a large, leaky one pays heavily for it. Choosing by property type is covered in heating by home type.

Fitting one: no flue or exterior wall needed, but use a certified electrician

Electric boilers do not need to be on an outside wall, unlike gas boilers, because there is no flue or gas pipe¹⁰. A wall-mounted electric boiler can be installed within a closet², which makes cupboards, internal walls and other space-saving locations possible. This siting freedom is one of the technology's genuine advantages in flats and small homes, and it removes the flue-positioning constraints described in boiler flues.

The rules around the work itself are straightforward. In England, planning permission is not normally required for the installation or replacement of a boiler or heating system if all the work is internal¹³. Building regulations still apply: if the installer is not on a Competent Persons Scheme, building regulations approval is needed from the council or a registered building control approver¹⁴. And the installer must be a qualified electrician, because the appliance is electrical rather than gas-fired¹⁰. The process end to end is covered in boiler installation, and the electrical requirements in electrical safety for electric heating.

On timing, boiler installations range from 4 to 6 hours for a like-for-like combi replacement up to 3 to 4 days where the heating system is being changed, with conversions between system types taking up to two days and full system upgrades with new pipework taking a few days depending on property size¹⁵. The householder needs to be at home during the work so the engineer has access to the boiler, the radiators and possibly the loft¹⁵. One electrical point deserves emphasis: changing fuel to an electric boiler is likely to require rewiring and possibly a new supply fuse¹⁰, so the electrical assessment is part of the job, not an afterthought.

Back-up and top-up: an electric boiler alongside a heat pump

An electric boiler is well suited to a supporting role as well as a starring one. Makers describe it as ideal for back-up heating that boosts an existing central heating system², and in hybrid heat pump systems the boiler provides exactly that function: additional support when demand is higher, such as during colder weather or when extra hot water is needed¹⁶.

A hybrid system pairs a heat pump, which runs cheaply and efficiently most of the year, with a second appliance that can cover the coldest days or the heaviest hot-water demand. The electric boiler variant of this pairing keeps the whole system free of combustion, which is not true of the more common gas-boiler hybrids. The trade-off is that the back-up runs on full-price electricity, so a system that leans on its back-up often will lean on the most expensive fuel in the house. The comparison between the two technologies on their own terms is in heat pumps vs boilers.

For a household planning a staged route off fossil fuels, this matters. An electric boiler can serve as an interim or bridging appliance, providing wet-system heating now from a system that a heat pump could later feed, since the radiators and pipework carry over. What it cannot do is reduce the home's dependence on grid electricity; it increases it, and the hybrid arrangement simply decides how much of that dependence is met by the efficient heat pump and how much by the resistance boiler.

Emissions and decarbonisation

At the point of use, an electric boiler produces no emissions: no flue gas, no carbon monoxide, no NOx at the appliance. The climate impact therefore depends entirely on the electricity supplying it. Worked examples from a Northern Ireland building regulations consultation illustrate how the fuel choices compare: an old oil-fired boiler with emissions of 0.298kg CO2 per kWh, an LPG boiler with 0.241kg CO2 per kWh, and a wood pellet boiler with 0.053kg CO2 per kWh¹⁷. Grid electricity's figure falls as the grid decarbonises, which is why electric heating's emissions improve over time without any change to the appliance.

The national picture is one of electrification. The Climate Change Committee's pathway has electrification and low-carbon electricity supply making up the largest share of emissions reductions, 60% by 2040¹⁸. At city level, Bristol's climate strategy calculates that around 160,000 boilers need to be replaced across the city to decarbonise heating¹⁹. Electric boilers are part of that replacement picture, particularly in homes where a heat pump is not practical, though policy weight is behind heat pumps: the Boiler Upgrade Scheme funds heat pumps and biomass, not electric boilers²⁰.

For the householder, the honest framing is this: an electric boiler removes combustion from the home and its emissions track the grid, so its climate performance improves automatically as the grid gets cleaner. What it does not remove is the dependence on the electricity supply and its price. A home heated electrically is only as decarbonised and as secure as the power station, the cable and the tariff behind it, which is the wider subject of heating and energy independence.

Looking after your boiler: upkeep, checks and safe operation

The general advice on servicing is annual: a boiler should be serviced every year to ensure it stays in good working order and maintains its efficiency¹⁴, and it is typically recommended that boilers are serviced on an annual basis²¹. The cost of a service varies with the type of boiler, its age, where you live and the company chosen²¹. The detail is in boiler servicing and maintenance.

One requirement does not apply here: the Gas Safe register. A Gas Safe registered engineer is the requirement for servicing gas boilers²¹, and an electric boiler has no gas components, so the work falls to a qualified electrician rather than a gas engineer. That said, the safety logic behind annual checks is not gas-specific. Incorrectly installed, poorly maintained or poorly ventilated household appliances, such as cookers, heaters and central heating boilers, are the most common causes of accidental exposure to carbon monoxide²². An electric boiler cannot produce carbon monoxide itself, but a home often contains appliances that can, which is covered in carbon monoxide safety.

The safety balance for an electric boiler is therefore different rather than simply better. On one side, no combustion means no flue gas, no gas leak risk from the appliance and no carbon monoxide production, and no annual Gas Safe visit. On the other, it is a high-power electrical appliance, and the installation and any maintenance must be done by someone qualified for electrical work¹⁰. The electrical side of that balance is covered in electrical safety for electric heating.

Financial support: VAT rules and grant coverage explained

The main government grant scheme does not fund electric boilers. The Boiler Upgrade Scheme provides upfront capital grants to support the installation of heat pumps and biomass boilers²⁰, with £5,000 available for biomass boilers in limited circumstances²³. It operates across England and Wales²⁴, and its grants assist with installation costs for low-carbon heating²⁵. Two scheme rules are worth knowing: an installation cannot be funded by more than one source of public funds, and applicants cannot have already received government funding or support for a heat pump or biomass boiler²⁶. The detail is in boiler and heating grants in England and Wales.

There are two partial exceptions worth checking. ECO4 Flex, an open scheme in Cambridgeshire and elsewhere, can fund low-carbon heating including energy-efficient boilers, heating controls and electric storage heaters for eligible households²⁷. And in Wales, the building regulations approved document lists the electric boiler alongside heat pumps, waste heat, geothermal heat, solar thermal and biofuels as a low-carbon heat source²⁸, which shapes how the technology is treated in new builds and major work.

The practical position for a householder is that an electric boiler is, at present, a technology you pay for yourself. The public money in home heating is directed at heat pumps, and the schemes that might touch an electric boiler are aimed at low-income or vulnerable households through energy-efficiency routes rather than at boiler replacement generally. Scotland and Northern Ireland have their own arrangements, covered in grants in Scotland and Northern Ireland.

Energy pricing, panels and why generating your own has limits

Because electricity is the fuel, the tariff is half the running cost. The most common electric meters for electric boilers are Economy 10 meters¹, and the £2,690 annual figure quoted earlier is an Economy 7 figure, against around £3,220 on a single-rate tariff⁴, which shows how much the tariff alone can move the annual bill. Off-peak tariffs reward homes that can store heat, which is why electric boiler systems usually include a large hot water tank¹. The tariff landscape is covered in Economy 7 and time-of-use tariffs.

Solar changes the picture again. Electric thermal store boilers can be powered using solar panels¹⁰, so a home with photovoltaics can meet part of its heating demand from its own roof. The tariff advice for homes with solar and a battery is either a dedicated solar and battery tariff, or a good export tariff matched with a dynamic import tariff or an Economy 7 tariff²⁹. A dedicated solar and battery tariff requires both solar panels and a battery²⁹, and the electrical works associated with solar installations fall under building regulations³⁰. Solar thermal, a different technology that heats water directly, is covered in solar thermal water heating.

The limits of self-supply should be stated as firmly as the promise. Winter, when heating demand peaks, is when solar generation is weakest, so a solar-powered electric boiler still leans on the grid for the bulk of its winter heat. A green import tariff changes the carbon content of the electricity bought, but not its price. What solar, a battery and a well-chosen tariff genuinely do is reduce the quantity of full-price grid electricity the boiler consumes, and in doing so they reduce, without removing, the home's dependence on suppliers and the grid. That is the realistic independence case for the electric boiler: not freedom from the electricity system, but a better position within it.