Electric boilers are good in the right home: they are compact, silent, need no gas supply or flue, and turn almost all the electricity they use into heat. The catch is that electricity costs over three times as much per unit as mains gas under Ofgem’s price cap, and an electric combi boiler gives a much weaker hot water flow than a gas combi, so they suit flats and small, well-insulated homes far better than family houses.

How an electric combi boiler works

An electric boiler looks like a small gas boiler and connects to your radiators in the same way. Inside, instead of a burner and heat exchanger, it has electric heating elements that warm the water as it passes through. A pump sends that water round the radiators, and an expansion vessel handles the change in volume as it heats up.

An electric combi boiler adds on-demand hot water. When you open a hot tap, the boiler switches its power to heating mains water instead of the radiators, just as a gas combi does. Some models add a small built-in hot water store to boost the flow for a few minutes.

Because nothing is burned, there is no flue, no condensate pipe and no risk of carbon monoxide. The boiler is close to 100 percent efficient at the point of use, and manufacturers point to very few moving parts and minimal servicing.

If you are weighing an electric boiler against a new gas boiler, our boiler installation team can survey your home and give you honest advice on what suits it.

The real limit: power and hot water flow

The biggest thing to understand about an electric combi is that its hot water is limited by how much power it can draw. Heating mains water by around 35 degrees, from cold to shower temperature, takes roughly 2.4kW for every litre per minute of flow. One manufacturer’s 14.4kW electric combi is rated at up to 7 litres per minute of continuous hot water. A mid-sized gas combi can deliver noticeably more, and larger ones considerably more.

That power also has to come from your electricity supply. Most homes have a single-phase supply with a main fuse that limits how much the whole house can draw at once. An electric boiler running flat out, an electric shower, an oven and an electric car charger all compete for the same supply. Before an electric boiler is fitted, an electrician should carry out a load assessment of the supply and the consumer unit. Sometimes the supply has to be upgraded by the network operator, which takes time and adds cost. Our electrical installations team can check your supply and consumer unit.

Electric combi vs gas combi vs heat pump

	Electric combi boiler	Gas combi boiler	Air source heat pump
Fuel	Electricity	Mains gas	Electricity
Heat produced per unit of energy used	About one unit	Slightly under one unit	Several units, from heat taken from the outside air
Cost per unit of energy	High	Low	High, but far less energy needed
Hot water	On demand, limited flow	On demand, stronger flow	Stored in a cylinder
Flue and gas pipe	Not needed	Needed	Not needed
Space	Compact, can go almost anywhere	Needs a flue route	Outdoor unit and a hot water cylinder
Annual gas safety check	Not needed	Recommended every year, and a legal duty for landlords	Not needed
Government grant	Not covered by the Boiler Upgrade Scheme	No	Boiler Upgrade Scheme in England and Wales
Best for	Flats and small homes without gas	Most homes on the gas grid	Well-insulated homes off gas or going low carbon

Pros of electric boilers

• No gas or flue needed. Ideal for flats where a flue route is impossible or there is no gas supply.
• Very compact and quiet. They can go in a kitchen cupboard, a hallway or a bedroom.
• No carbon monoxide risk. There is no combustion, so no flue gases.
• Simple and reliable. Fewer moving parts than a gas boiler, and less to go wrong.
• High efficiency at the point of use. Almost every unit of electricity becomes heat in the water.
• Lower carbon over time. As the electricity grid gets cleaner, so does the heat.

Cons of electric boilers

• Higher running costs. Under Ofgem’s price cap, electricity costs over three times as much per unit as gas, and a gas boiler turns most of its gas into heat, so heating with direct electricity usually costs much more.
• Weaker hot water. One shower at a time is realistic. Two outlets at once will struggle.
• Output limits. A single-phase home supply caps how big the boiler can be, which rules out large houses with a high heat demand.
• Supply upgrades. Some homes need a bigger supply or a new consumer unit before one can be fitted.
• No grant. The Boiler Upgrade Scheme funds heat pumps and biomass boilers, not electric boilers.

Who should consider an electric combi boiler

An electric combi makes sense when most of these are true:

1. The property is a flat, an annexe or a small, well-insulated house.
2. There is no gas supply, or getting a flue out is impossible or very expensive.
3. Only one or two people live there, and one shower at a time is enough.
4. A heat pump is not practical, for example because there is nowhere for the outdoor unit.
5. The electricity supply can take the load, or can be upgraded.

If you have gas and a normal family house, a modern gas combi or system boiler will almost always be cheaper to run and give better hot water. Our guide to the best combi boilers explains the options. If your current gas boiler is simply getting old rather than unsuitable, our article on how long a boiler lasts will help you decide whether to replace it like for like.

Landlords and electric boilers

An electric boiler does not need an annual gas safety certificate, which is one reason landlords of flats consider them. The electrical installation still needs an electrical safety check. In England, private landlords must have the electrics inspected and tested at least every five years, which our EICR electrical safety certificate service covers.

How we price it

Installations are quoted as a fixed price after a free survey, so the price you agree is the price you pay. For a gas boiler, you can get your price online in a couple of minutes with our boiler quote tool. Our rates for electrical work, repairs and servicing are published on our prices page.

Frequently asked questions

Is it worth getting an electric combi boiler?

It is worth it for small flats and homes without gas, where it avoids a flue and a gas supply altogether. For most family homes on the gas grid, a gas combi is cheaper to run and gives much better hot water.

What are the disadvantages of an electric combi boiler?

The main ones are higher running costs than gas, weaker hot water flow, and a power limit set by your electricity supply. Some homes also need a supply or consumer unit upgrade before one can be fitted.

Can an electric combi run two showers at once?

Realistically, no. The hot water flow depends on the power the boiler can draw, and even a large electric combi struggles to supply two outlets at once. A home with two bathrooms in use together needs a different solution.

Do electric boilers need servicing?

They need less than gas boilers and no gas safety check, but manufacturers still recommend regular checks of the electrical connections, pressure, expansion vessel and system water. Follow the manufacturer’s instructions to keep the warranty valid.

Is an electric boiler better than a heat pump?

An electric boiler is cheaper and simpler to install, but a heat pump uses far less electricity for the same heat because it collects heat from the outside air. Over the life of the system, a heat pump usually costs less to run in a well-insulated home.

Honest heating advice in Hertfordshire, Bedfordshire and Cambridgeshire

If you are deciding between an electric combi, a new gas boiler or another option, our engineers can look at your home, your supply and how you use hot water, and tell you straight what will work. Start with our boiler installation page or call 01462 506374, answered 24 hours a day, 7 days a week.