The short answer
Both run on electricity, but the efficiency gap is large. An electric boiler heats water by passing electricity through an element — it is around 99 to 100% efficient, so one unit of electricity gives one unit of heat. A heat pump moves heat from the outside air rather than generating it, achieving a SCOP of around 3 to 4 — 3 to 4 units of heat per unit of electricity. For the same heat, a heat pump therefore uses roughly a third of the electricity, making it far cheaper to run. An electric boiler is cheaper and simpler to install — it is compact, needs no outdoor unit and works with existing radiators — which can suit flats and low-demand homes. But on running cost, a heat pump wins clearly, and it qualifies for the £7,500 Boiler Upgrade Scheme grant where an electric boiler does not.
Electric boilers are sometimes proposed as a simple way to drop the gas connection, but they are expensive to run. Here is how they compare with a heat pump.
Heat pump vs electric boiler
- Heat pump efficiencySCOP ~3.0–4.0
- Electric boiler efficiency~99–100%
- Electricity for same heatHeat pump uses ~1/3
- InstallHeat pump higher; electric boiler lower
- BUS grantHeat pump yes; electric boiler no
Why the running-cost gap is so wide
An electric boiler is a direct electric heater: electricity flows through an element and heats water for your radiators and taps. Like all resistance heating it is essentially 100% efficient at the point of use — but that is the ceiling. One unit of electricity in produces one unit of heat out.
A heat pump does not make heat by resistance. It uses a refrigeration cycle to move heat from the outside air into your home, so it delivers more heat energy than the electricity it consumes. A SCOP of 3 to 4 means 3 to 4 units of heat per unit of electricity. Run the two side by side on the same tariff and the heat pump uses roughly a third of the electricity for the same warmth — which is why electric boilers, despite their simplicity, are one of the more expensive ways to heat a home.
| Factor | Air source heat pump | Electric boiler |
|---|---|---|
| How it makes heat | Moves heat from outside air | Direct electric resistance |
| Efficiency | SCOP ~3.0–4.0 | ~99–100% |
| Electricity for same heat | Roughly one third | Three times as much |
| Running cost | Lower | High |
| Outdoor unit | Yes | No |
| Hot water cylinder | Usually required | Optional / model-dependent |
| BUS grant | £7,500 | Not eligible |
Indicative comparison for guidance. Sources: Energy Saving Trust.
Installation, space and simplicity
An electric boiler scores on simplicity. It is a compact wall-mounted unit with no combustion, no flue, no gas supply and no outdoor equipment. It connects to existing radiators and can fit where a gas boiler used to sit, which makes installation cheap and quick — useful in flats or where outdoor space is tight.
A heat pump is a larger undertaking: an outdoor unit, a hot water cylinder, and often radiator upgrades to suit the lower flow temperature. That raises the up-front cost and needs more space and planning. The £7,500 Boiler Upgrade Scheme grant offsets much of the difference for eligible homes — and electric boilers do not qualify for it.
Electrical supply and demand on the grid
One practical difference between the two is how much electrical load they place on the home and the network. A heat pump for a typical house draws a modest electrical load because it multiplies its input energy, so it usually works within a standard domestic supply. An electric boiler sized to heat the same house must deliver all that heat directly, so it draws a much larger current — which can require a higher-rated supply and, in some cases, a supply upgrade.
That higher demand also matters at the national level. Because electric boilers use roughly three times the electricity of a heat pump for the same heat, widespread use of direct electric heating would place far greater strain on the grid, especially during cold-weather peaks. Heat pumps deliver the same comfort with a fraction of the electrical demand, which is one reason policy and grant support favour them.
For an individual homeowner, the immediate implication is that a heat pump is more likely to run on the existing supply, while a whole-house electric boiler may need an electrician to confirm the supply can handle the load before installation.
Carbon and the bigger picture
Both systems run on electricity, so both get cleaner as the grid decarbonises. But because a heat pump uses far less electricity for the same heat, its carbon footprint per unit of warmth is much lower than an electric boiler's — roughly a third, mirroring the efficiency difference.
For a household leaving gas, oil or LPG behind, the choice between an electric boiler and a heat pump is largely a trade-off between a low install cost now and much lower running and carbon costs over the life of the system. An MCS-certified installer can carry out a heat loss survey to confirm a heat pump will keep the home warm and what, if any, radiator or insulation upgrades are needed before committing.
Frequently asked questions
Is a heat pump cheaper to run than an electric boiler?
Yes, clearly. An electric boiler is around 100% efficient, so one unit of electricity gives one unit of heat. A heat pump delivers 3 to 4 units of heat per unit of electricity, so it uses roughly a third of the electricity for the same heat. On the same tariff, a heat pump is far cheaper to run than an electric boiler.
Can I get a grant for an electric boiler?
No. The Boiler Upgrade Scheme grant of £7,500 applies to air source and ground source heat pumps (and biomass boilers in some rural cases), not to electric boilers. If you want grant support, a heat pump is the eligible route, provided the property meets the EPC requirement and the work is done by an MCS-certified installer.
When does an electric boiler make more sense than a heat pump?
In a small, very well-insulated flat or a property where there is no way to site an outdoor unit, an electric boiler's simplicity and low install cost can outweigh its higher running cost. For most homes with normal heat demand, a heat pump's much lower running cost makes it the better long-term choice.
Sources & further reading
- Energy Saving Trust — air source heat pumps
- Energy Saving Trust — electric heating
- Ofgem — Boiler Upgrade Scheme
Figures on this page are typical UK ranges drawn from published sources and depend on your specific home. They are guidance, not a quotation or guaranteed saving.