Oil Boiler vs Air Source Heat Pump: Which Is Right for a Pembrokeshire Home?
Both can heat an off-gas-grid home, but they work differently. The right choice depends on your property, budget, existing system and what you want from the heating over the coming years.
Last updated: 22 August 2026. Fuel prices, tariffs and grant rules can change.
The short answer
Replacing an oil boiler with another oil boiler is usually the more familiar route and may involve fewer changes to the heating system. An air source heat pump can provide a lower-carbon alternative with no oil tank or fuel deliveries, but it needs a proper survey and may require radiator, hot-water or electrical work.
Neither option is automatically right for every home. A balanced decision should compare the complete installation, likely operation and long-term priorities—not just the price of the appliance.
Oil boiler and heat pump compared
| Consideration | Oil boiler | Air source heat pump |
|---|---|---|
| Energy source | Burns stored heating oil. | Uses electricity to move heat from the outside air into the home. |
| Heat delivery | Often runs radiators at higher water temperatures. | Normally designed for steady heating at lower flow temperatures. |
| Fuel storage | Requires a suitable oil tank and fuel deliveries. | No oil tank, but needs a suitable outdoor unit position. |
| Hot water | Available through combi, system or regular boiler arrangements. | Most whole-home systems use a suitable hot-water cylinder. |
| Heating-system changes | A like-for-like replacement may reuse much of the existing system, subject to condition and design. | Radiators, pipework, controls and electrical supply must be checked as part of the design. |
| Upfront support | No Boiler Upgrade Scheme contribution for a replacement oil boiler. | Eligible installations can receive a fixed Boiler Upgrade Scheme contribution. |
| Best suited to | Homes wanting a familiar system or where a heat pump is not currently practical. | Suitable homes where the owner wants to move away from oil and accepts a designed low-temperature system. |
Running-cost warning: no installer can promise savings from the heating technology alone. Results depend on oil prices, electricity tariff, heat demand, system efficiency, controls, hot-water use and how the home is heated.
How an air source heat pump works
A heat pump uses electricity to operate a refrigeration cycle that collects energy from the outside air and transfers it into water for the heating system. Because it moves heat rather than creating all of it from fuel, a well-designed system can deliver several units of heat for each unit of electricity used.
Real-life efficiency changes with outdoor temperature, water temperature, radiator sizing and system design. Lower flow temperatures generally support better efficiency, which is why room-by-room heat loss and emitter sizing are so important.
Designed, not swapped
A heat pump is not simply a boiler replacement. The whole heating system is assessed and designed around the home.
Steady comfort
Heat-pump heating is normally set up to maintain a stable temperature rather than deliver short blasts of very hot water.
What could the heat-pump grant contribute?
Under current Boiler Upgrade Scheme guidance, an eligible off-gas-grid property replacing oil or LPG can receive up to £9,000 towards an eligible air-to-water or ground-source heat pump. Other eligible installations can receive £7,500.
The higher amount became available on 21 July 2026 and is currently due to remain available until 31 March 2027. The grant is a fixed contribution and may not cover the whole project. The MCS installer applies on the property owner’s behalf, and Ofgem confirms consent and eligibility.
When replacing the oil boiler may be the practical choice
- You need a straightforward replacement quickly and major heating-system changes are not practical.
- The property has no suitable heat-pump position or hot-water cylinder space.
- The electrical supply or building work required makes a heat pump unsuitable at present.
- You prefer the familiar operation of an oil boiler and accept continued fuel deliveries and tank maintenance.
- A proper heat-pump assessment shows that the proposed project is not viable for the property or budget.
Even with a replacement boiler, the existing system, controls, flue, oil supply and tank should be assessed rather than assuming a simple appliance swap.
When a heat pump is worth serious consideration
- You want to move away from oil storage and fuel deliveries.
- The home has a practical outdoor location and space for the required hot-water equipment.
- You are prepared to consider targeted radiator or system upgrades where the calculations show they are needed.
- The property may qualify for the Boiler Upgrade Scheme contribution.
- You want a designed low-carbon heating system with local installation and aftercare.
Oil boiler and heat pump questions
Is a heat pump always cheaper to run than oil?
No. Running costs depend on oil and electricity prices, the electricity tariff, seasonal system efficiency, heat demand and how the heating is controlled. A newer efficient oil boiler may not automatically cost more to run.
Will a heat pump heat the home properly in winter?
A correctly sized system should meet the calculated space-heating requirement at the selected local winter design temperature. The survey and system design are therefore critical.
Will I need a new hot-water cylinder?
Most whole-home air-to-water systems require a suitable cylinder. An existing cylinder may not have the correct coil or capacity, so it must be assessed during the survey.
Do all radiators need replacing?
No. Each radiator is checked against its room’s calculated heat loss at the proposed flow temperature. The quotation should identify only the changes needed.
Can a private landlord apply for the grant?
Yes, private landlords can use the Boiler Upgrade Scheme when the property and installation meet the eligibility requirements.
Get a property-specific comparison
Del Brace Plumbing & Heating installs oil boilers and MCS-certified air source heat-pump systems, so the advice can focus on what suits the property rather than forcing one option.
- MCS-registered heat pump installer
- Worcester Bosch accredited boiler installer
- Room-by-room heat-loss calculations
- Clear installation quotations
- BUS application support where eligible
- Local service across Pembrokeshire
Read current general guidance from Energy Saving Trust and the current grant process from Ofgem.
