The short answer
For a home off the gas grid, the choice is usually between keeping an oil boiler and switching to an air source heat pump. An oil boiler burns kerosene to produce high-temperature water, has a low up-front cost and works with existing radiators, but oil prices are volatile, the system is a fossil fuel, and you need a tank and regular deliveries. A heat pump runs on electricity, produces lower carbon emissions, and is often cheaper to run than oil because it delivers around 3 units of heat per unit of electricity (a SCOP of roughly 3 to 4). It costs more to install, but the Boiler Upgrade Scheme grant of £7,500 closes much of that gap. The main trade-off is that a heat pump runs at lower flow temperatures, so radiators and insulation may need upgrading in an older property.
Off-gas-grid homes have historically relied on oil-fired heating, but heat pumps are now a serious alternative. Here is how the two compare across the factors that actually affect the decision.
Heat pump vs oil — at a glance
- Heat pump fuelElectricity (renewable-capable)
- Oil boiler fuelKerosene (heating oil)
- Typical heat pump SCOPAround 3.0 to 4.0
- Oil boiler efficiencyAround 90 to 93%
- BUS grant for heat pump£7,500 (England & Wales)
Running costs and efficiency
An oil boiler is typically 90 to 93% efficient — it converts almost all the energy in the kerosene into heat. A heat pump works differently: it moves heat from the outside air rather than burning fuel, so it can deliver more heat energy than the electrical energy it consumes. A well-designed air source heat pump achieves a seasonal coefficient of performance (SCOP) of roughly 3 to 4, meaning 3 to 4 units of heat for each unit of electricity.
Whether the heat pump is cheaper to run depends on the price of electricity relative to oil. Electricity costs more per unit than heating oil, but the heat pump's efficiency offsets that. In many cases a heat pump running on a standard tariff comes out similar to or cheaper than oil, and a heat-pump-friendly time-of-use electricity tariff can widen the gap further. Oil prices are also volatile — they track global crude markets and can swing sharply, which makes budgeting harder than for a fixed electricity tariff.
| Factor | Air source heat pump | Oil boiler |
|---|---|---|
| Fuel | Electricity | Kerosene (heating oil) |
| Typical efficiency | SCOP ~3.0–4.0 | ~90–93% |
| Running cost | Often similar to or below oil | Volatile, tracks crude oil |
| Carbon emissions | Low and falling as grid decarbonises | High (fossil fuel) |
| Up-front cost | Higher (grant available) | Lower |
| Fuel storage | None | Oil tank required |
Indicative comparison for guidance. Sources: Energy Saving Trust; MCS.
Installation, servicing and the oil tank
An oil boiler swap is cheaper and simpler to install than a heat pump — it reuses existing radiators and pipework and the unit itself is compact. A heat pump installation is more involved: it requires an outdoor unit, a hot water cylinder (most homes that had a combi or system boiler will need one), and often radiator upgrades to suit the lower flow temperature.
On servicing, both need an annual check. An oil boiler service includes cleaning the burner and checking combustion; you also remain responsible for an oil tank, which has its own safety and environmental rules and an eventual replacement cost. A heat pump has no combustion, no flue and no fuel tank — servicing is generally lighter, though it does involve a refrigerant circuit that must be checked.
Switching to a heat pump also lets you remove the oil tank entirely, freeing up space and removing the risk of an oil leak, which can be expensive to remediate.
Carbon, future-proofing and suitability
Heating oil is a fossil fuel, so an oil boiler's carbon emissions are fixed and high. A heat pump's emissions depend on the electricity grid, which continues to decarbonise — so the same heat pump gets cleaner over time without any change to the equipment.
The government has signalled a long-term direction away from fossil-fuel heating, and off-gas-grid oil homes are part of that conversation. While there is no confirmed ban date that homeowners need to act on today, the trajectory favours electrified heating.
Suitability is the deciding factor for many older off-grid properties. A heat pump performs best with good insulation and adequately sized radiators or underfloor heating. A solid-wall cottage with small radiators may need fabric and emitter upgrades to run a heat pump efficiently — an MCS-certified installer carries out a heat loss survey to confirm what is needed. An oil boiler, by contrast, will heat almost any property as-is, which is why it remains common in hard-to-treat homes.
Frequently asked questions
Is a heat pump cheaper to run than oil?
It can be, but it depends on electricity and oil prices at the time. A heat pump's high efficiency (SCOP around 3 to 4) offsets the higher per-unit cost of electricity, so running costs are often similar to or below oil — and a heat-pump-friendly time-of-use tariff improves the comparison further. Oil prices are volatile, which makes a heat pump's costs more predictable.
Can I get a grant to replace my oil boiler with a heat pump?
Yes. The Boiler Upgrade Scheme offers £7,500 towards an air source heat pump in England and Wales, and off-gas-grid oil homes are eligible. The property needs a valid EPC with no outstanding insulation recommendations, and the work must be done by an MCS-certified installer. Scotland has its own funding through Home Energy Scotland.
Will a heat pump heat an old off-grid house as well as my oil boiler?
It can, but a heat pump runs at lower flow temperatures than an oil boiler, so it relies more on good insulation and correctly sized radiators or underfloor heating. An older property may need fabric or radiator upgrades. An MCS installer carries out a heat loss survey to design a system that keeps the home warm; for some hard-to-treat homes a hybrid system is worth considering.
Sources & further reading
- Energy Saving Trust — air source heat pumps
- Ofgem — Boiler Upgrade Scheme
- MCS — find an installer and how heat pumps work
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.