Glossary · Boilers and boiler types
What is an electric boiler?
An electric boiler heats the water for radiators, and sometimes a hot water cylinder, using electricity instead of burning a fuel. It has no flue, so it can go where a flue is not possible. Manufacturers quote efficiency near 100%, but electricity costs more per unit than gas.
Key points
- An electric boiler has no flue, so it suits homes such as tower blocks where a flue is not an option.
- It is a wet system: it works with standard radiators, pumps, programmers and thermostatic radiator valves.
- Baxi quotes 99.8% efficiency for some models, and Approved Document L treats electric resistance heating as 100% efficient.
- Baxi says electric boilers are far more energy efficient than gas boilers, but electricity is more expensive to buy.
- Replacing an electric boiler with a heat pump can qualify for a Boiler Upgrade Scheme grant, because electric counts as a fossil fuel system there.
How an electric boiler works
An electric boiler heats the water in a central heating circuit with electricity. It does not burn anything, so it has no flue.[1]Baxi, What are the different types of boilers? Baxi describes its electric boilers as highly efficient and low maintenance, and says they suit homes off the mains gas network.[2]Baxi, Electric boilers
The rest of the system looks familiar. Baxi says its Amptec model gives controllable wet central heating with standard radiators, programmers, circulating pumps, room thermostats and thermostatic radiator valves.[3]Baxi, Amptec electric boiler There is also a version for underfloor heating.[2]Baxi, Electric boilers The water heated by the boiler goes round the radiators, just as with a gas boiler.
Models and what they do
| Baxi model | Output options | What it is |
|---|---|---|
| Amptec | 4, 6, 9, 11 and 12 kW | Compact boiler for radiators |
| Amptec S | 4, 6, 8, 12, 14 and 18 kW | Radiator or underfloor systems, with modulating heat |
| Electromax | 6 or 9 kW | Boiler plus 180 litre cylinder in one case |
Those figures come from Baxi’s own product pages.[3]Baxi, Amptec electric boiler[4]Baxi, Amptec S electric boiler[5]Baxi, Electromax electric boiler Other makers offer their own ranges, so check the manufacturer for the model you are offered. For how output relates to home size, see boiler size.
Baxi says the Amptec S can modulate heat, so it produces only the right amount to keep a steady temperature, which reduces running costs.[4]Baxi, Amptec S electric boiler It quotes 99.8% efficiency for the Amptec and Electromax.[3]Baxi, Amptec electric boiler[5]Baxi, Electromax electric boiler Approved Document L goes further for design purposes. It assumes electric resistance heating is 100% efficient, so it sets no minimum efficiency for these systems.[6]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments
Running cost and carbon
Efficiency is not the same as cost. Baxi says electric boilers are much more energy efficient than gas boilers, but electricity is more expensive to buy.[1]Baxi, What are the different types of boilers? The balance depends on your tariff and how much heat the house needs. We do not quote running costs here because they change with energy prices.
Government grant rules treat electric boilers as a fossil fuel heating system for replacement. The Boiler Upgrade Scheme says fossil fuel heating systems include oil, gas, electric or LPG.[8]Department for Energy Security and Net Zero, Apply for the Boiler Upgrade Scheme: overview It offers £7,500 towards an air source heat pump or ground source heat pump.[7]Department for Energy Security and Net Zero, Apply for the Boiler Upgrade Scheme: what you can get See our boiler grants page and heat pumps.
Example
Hannah owns a one-bedroom flat in a Leeds tower block with no gas supply and no way to fit a flue. An electric boiler suits that building because it needs no flue.[1]Baxi, What are the different types of boilers? She picks a model with an output sized to the flat, and keeps standard radiators with a programmer and room thermostat.[3]Baxi, Amptec electric boiler Her yearly cost will follow her electricity tariff, not the boiler’s efficiency figure.
What people get wrong
People hear 99.8% efficient and assume the bills will be low. Efficiency measures how much of the electricity becomes heat. It says nothing about the price of that electricity, which Baxi says is more expensive to buy than gas.
Baxi makes the price point itself.[1]Baxi, What are the different types of boilers? The other common error is to treat an electric boiler as a heat pump. It is not. An electric boiler makes one unit of heat for roughly one unit of electricity. A heat pump moves heat from outside, so it can deliver more heat than the electricity it uses. Read heat pump vs gas boiler and electric heating for the comparison.
The bottom line
An electric boiler is a flueless boiler that heats radiators, and sometimes a cylinder, with electricity. It suits flats, off-gas homes and places where a flue is impossible. It is close to 100% efficient, but electricity costs more than gas, so running cost needs checking against your tariff.
Common questions
Does an electric boiler need a flue?
No. Baxi says electric boilers do not have a flue, so they suit homes where a flue is not an option, such as tower blocks. There is no combustion, so there are no exhaust gases to vent.
Is an electric boiler cheaper to run than a gas boiler?
Not usually. Baxi says electric boilers are much more energy efficient than gas boilers, but electricity is more expensive to buy. Running cost depends on your tariff, so compare unit prices for your home.
Can an electric boiler work with radiators?
Yes. Baxi says its Amptec model provides controllable wet central heating with standard radiators, programmers, circulating pumps, room thermostats and thermostatic radiator valves.
Can an electric boiler heat my hot water too?
Some can. Baxi's Electromax combines an electric boiler with a 180 litre hot water cylinder in one airing cupboard-sized case. Other electric boilers heat radiators only.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- Baxi. What are the different types of boilers?. Checked 11 November 2026. ↩
- Baxi. Electric boilers. Checked 11 November 2026. ↩
- Baxi. Amptec electric boiler. Checked 11 November 2026. ↩
- Baxi. Amptec S electric boiler. Checked 11 November 2026. ↩
- Baxi. Electromax electric boiler. Checked 11 November 2026. ↩
- Ministry of Housing, Communities and Local Government. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments. Checked 11 November 2026. ↩
- Department for Energy Security and Net Zero. Apply for the Boiler Upgrade Scheme: what you can get. Checked 11 November 2026. ↩
- Department for Energy Security and Net Zero. Apply for the Boiler Upgrade Scheme: overview. Checked 11 November 2026. ↩