The short version
- Against mains gas, a heat pump is close. A well-designed one saves modestly; a badly designed one costs more.
- The number that decides it is SCOP — how many units of heat you get per unit of electricity. Below about 2.8 on a standard tariff, you lose.
- A heat-pump electricity tariff changes the answer more than the hardware does.
- Against oil or LPG, it is not close. The heat pump wins comfortably.
This is the question we get asked most, and it has an uncomfortable answer: against mains gas, at standard electricity prices, a heat pump saves less than most people expect. Some installations do not save anything.
That is worth saying plainly, because the alternative — promising savings that do not arrive — is how the industry has damaged its own reputation. Here is the arithmetic.
The prices we are working from
Ofgem's price cap for 1 July to 30 September 2026:
| Unit rate | Standing charge | Standing charge per year | |
|---|---|---|---|
| Electricity | 26.11p / kWh | 57.19p / day | £209 |
| Gas | 7.33p / kWh | 29.04p / day | £106 |
Note the ratio: electricity costs about 3.6 times as much as gas per kWh. That single number is why this comparison is tight. A heat pump has to be more than 3.6 times as efficient as your boiler just to break even on fuel.
The number that decides everything
A gas boiler cannot exceed 100% efficiency. A modern condensing boiler is rated around 92%, but in a real house, running at real flow temperatures, 85% is a fair working figure.
A heat pump moves heat rather than making it, so it can exceed 100%. Its seasonal efficiency is called SCOP — Seasonal Coefficient of Performance. A SCOP of 3.2 means 3.2 kWh of heat for every 1 kWh of electricity.
SCOP is not a fixed property of the unit. It depends on how the system is designed, and mostly on flow temperature. Run a heat pump at 35°C into generously sized radiators or underfloor heating and you might see 4.0. Run the same unit at 55°C because the radiators were never upgraded and you might see 2.5. Same hardware, completely different bill.
The comparison
Take a home needing 12,000 kWh of heat and hot water a year — a reasonable figure for a typical three-bedroom UK house.
| Scenario | Energy used | Annual cost | vs gas boiler |
|---|---|---|---|
| Gas boiler at 85% efficiency | 14,118 kWh gas | £1,141 | — |
| Heat pump, SCOP 2.5, standard tariff | 4,800 kWh elec | £1,253 | +£112 |
| Heat pump, SCOP 3.2, standard tariff | 3,750 kWh elec | £979 | −£162 |
| Heat pump, SCOP 4.0, standard tariff | 3,000 kWh elec | £783 | −£358 |
| Heat pump, SCOP 3.2, heat-pump tariff (~15p) | 3,750 kWh elec | £563 | −£578 |
The gas figure includes the £106 annual gas standing charge, which disappears if you remove gas from the property entirely. The electricity standing charge is paid either way, so it is excluded from both.
What that table actually says
- At SCOP 2.5, you lose. That is not a hypothetical — it is what you get from a heat pump dropped into an unmodified system running high flow temperatures. It is the most common way these installations disappoint.
- At SCOP 3.2 on a standard tariff, you save about £162 a year. Real, but modest — around 14%. Nobody should be buying a heat pump on that number alone.
- The tariff is worth more than the hardware upgrade. Moving from SCOP 3.2 to 4.0 saves £196. Moving from a standard tariff to a heat-pump tariff at the same SCOP saves £416. Most homeowners spend a great deal of time on the first and none on the second.
Where these figures could be wrong for you. Heat demand varies enormously — a well-insulated modern house might need 7,000 kWh, a large solid-wall Victorian house 20,000. The price cap changes quarterly, and the next revision takes effect on 1 October 2026. Heat-pump tariffs have conditions attached and are not open to everyone. Treat this as the shape of the answer, not your answer.
Against oil and LPG it is a different conversation
Everything above concerns mains gas, which is the cheapest fuel per kWh in Britain by a wide margin. If you heat with oil or LPG, the comparison is far more favourable, and it is also more volatile — oil prices are not capped, and off-grid households absorbed sharp increases through 2025 and 2026.
Off-grid oil and LPG homes are also currently eligible for a £9,000 grant rather than £7,500, which lands until 31 March 2027. Better running-cost case and more capital support, in the same window.
How to end up on the right row of that table
The difference between the losing row and the best row is about £690 a year, every year. It comes down to four things:
- A proper heat loss calculation, room by room. Not a rule of thumb, not a figure based on your old boiler's output. This is the foundation, and skipping it is the single most common cause of poor performance.
- Emitters sized for low flow temperatures. Usually this means some radiators get bigger. If a quote involves no radiator changes at all, ask exactly what flow temperature the design assumes.
- Weather compensation enabled and set up properly, so the flow temperature tracks the outside temperature instead of running flat out.
- A heat-pump electricity tariff. Worth more than any of the above, and frequently forgotten once the installation is signed off.
Where ByEco stands right now. Boiler Upgrade Scheme applications can only be submitted by an MCS-certified installer. ByEco is currently going through MCS and TrustMark certification, so we cannot lodge a BUS application for you yet. If you are planning work, talk to us about timing — we will tell you honestly whether we can help on your schedule or whether you are better off going elsewhere.
The verdict
Against mains gas, a heat pump is a good decision if the system is designed properly and you move to a suitable tariff, and a poor one if either is neglected. The grant makes the capital cost work; the design and the tariff make the running cost work. They are separate problems and both have to be solved.
Against oil or LPG, it is straightforwardly a good decision, and the current grant window makes it a notably good one.
Anyone who tells you a heat pump will halve your bills without asking about your radiators has not done the arithmetic.
Sources
Every figure on this page was checked against primary sources on 22 August 2026. Grant rules and energy prices change — if you are reading this much later, verify before acting.
- Ofgem — Energy price cap unit rates and standing charges
- Ofgem — Energy price cap
- Ofgem — Boiler Upgrade Scheme (BUS)
Talk it through
Every home is different, and the honest answer to “is this worth it?” depends on your heat demand, your insulation and your tariff. Send us your postcode and we will give you a realistic figure rather than a hopeful one.
