Can an oil boiler be replaced by a heat pump?
Yes, and oil-heated houses are among the homes where the switch is most common. An air-to-water heat pump does the same job as the boiler: it heats water for radiators and for a hot water cylinder. A ground source heat pump does the same, drawing heat from pipes buried in the garden rather than from the outside air. Most oil homes already have radiators and pipework, so the heat pump connects into a system that is broadly familiar.
What decides whether it works well is not the fuel you are leaving behind, but the house itself. A heat pump runs at lower water temperatures for longer, so the property’s heat loss, the size of the radiators and the space for a cylinder matter more than they did with oil. Our guide to whether a home is suitable for a heat pump explains those checks in detail.
What changes in the heating system
The pipes and many of the radiators can stay. Almost everything that makes and stores heat changes.
| Oil heating | Heat pump | |
|---|---|---|
| Where the heat comes from | Burning heating oil in a boiler, indoors or in an outdoor casing | An outdoor unit (air source) or buried pipes (ground source), run on electricity |
| Fuel storage | An oil tank, with deliveries to arrange | None. The electricity supply is checked instead |
| Water temperature | Designed to run hotter, for shorter periods | Designed to run cooler, for longer periods |
| Hot water | From the boiler, via a cylinder or directly if it is an oil combi | Almost always a hot water cylinder, sized for the heat pump |
| Controls | Boiler timer and room thermostat | Heat pump controls, often with weather compensation |
| Outside | The tank, and sometimes the boiler itself | The outdoor unit, with clear space around it |
The practical upshot is that the job has three parts: taking the oil system out, designing and fitting the heat pump system, and adjusting the radiators and hot water to suit it.
What happens to the oil boiler
The boiler is disconnected, drained and removed, along with its flue and the oil supply pipe from the tank. This is normally part of the installer’s quote, so check that the quote says so.
If the Boiler Upgrade Scheme is paying towards the heat pump, the oil boiler has to go. The scheme requires the existing fossil-fuel heating to be fully replaced, so it cannot stay connected as a backup for cold spells. That surprises some people who expected to keep it “just in case”.
Removing the boiler often frees space. In a kitchen or utility room, that space is sometimes where the new cylinder or the heat pump’s indoor controls end up.
What happens to the oil tank
The tank is the part of an oil system that people most often forget to ask about. Once the heat pump is running, the tank serves no purpose, and leaving oil sitting in it is a pollution risk.
Emptying it
Any oil left in the tank, and the sludge that settles at the bottom, has to be removed and disposed of properly. That is specialist work. The easiest saving is to run the tank down before installation day: order smaller top-ups in the weeks beforehand rather than a full delivery.
Taking it away or making it safe
Most people have the tank removed once it is empty. A plastic tank can usually be cut up and taken away; a steel or concrete tank, or one that is buried, is a bigger job. Where removal is impractical, the tank can be cleaned and made safe instead. Either way, agree in writing who is responsible, what it costs and when it happens. Some installers include it; others arrange a specialist.
The space the tank leaves
An empty tank base can look like the obvious place for the outdoor unit. Sometimes it is. But the unit needs good airflow, a sensible distance to the cylinder and neighbours, and a solid, level base. The installer decides where it goes on those grounds, not on where the tank happened to be.
Radiators and the hot water cylinder
Radiators. An oil boiler normally heats the radiator water hotter than a heat pump would. At a lower temperature a radiator gives out less heat, so rooms where the existing radiator is only just big enough may need a larger one, or a different type. The heat-loss survey identifies those rooms individually. Pipework is checked too. Very narrow (microbore) pipes can limit how much warm water reaches each radiator.
Hot water. Many oil homes already have a hot water cylinder. It may still need replacing, because a heat pump needs a cylinder with a larger internal coil to heat the water efficiently. If you have an oil combi boiler, and so no cylinder at all, finding space for one is usually the first practical question: an airing cupboard, a loft or a utility room are the usual candidates.
The heat-loss survey
Every sensible heat pump design starts with a heat-loss calculation for each room. It uses the construction of the walls, windows, floors and roof, and the room sizes, to work out how much heat each room needs on a cold day. From that the installer sizes:
- the heat pump itself;
- each radiator, or underfloor heating where it is fitted;
- the hot water cylinder;
- the pipework between them.
Older rural properties are where this matters most. Solid stone walls, extensions of different ages and big rooms all behave differently. An installer who quotes without measuring each room is guessing. A good survey may also point out that some insulation or draught-proofing would let a smaller heat pump do the job.
Where the outdoor unit goes
An air source unit sits outside on a level base, usually against a wall or on the ground nearby. The installer looks at:
- Airflow. The unit needs clear space in front of and around it.
- Distance to the cylinder. Shorter pipe runs are better.
- Noise. Distance from bedroom windows, including the neighbours’.
- Planning. Many installations fall under permitted development, but conditions apply, and listed buildings and conservation areas are handled differently. The installer checks what applies to your property.
Rural oil homes often have more outdoor space than town houses, which makes siting easier. It also makes ground source a realistic option to discuss, where there is enough land or room for a borehole.
The grant for oil-heated homes
The Boiler Upgrade Scheme covers the replacement of oil heating with an eligible heat pump in England and Wales. For a limited period there is a higher value for homes that are off the mains gas grid:
Enhanced off-gas grant
£9,000
For homes off the mains gas grid, as the scheme defines it, replacing oil or LPG heating with an air-to-water or ground source heat pump.
For applications properly made by
Not every oil-heated home meets that definition. A capped gas meter, for example, means the property still counts as connected to mains gas, and the standard £7,500 may apply instead. Our step-by-step guide explains how to check whether your home is off the gas grid. The full conditions, exclusions and dates are on our off-gas heat pump grant page. If your home runs on LPG rather than oil, the tank and supplier questions differ, and our guide to replacing an LPG boiler covers them.
Either way, the grant is claimed by your MCS-certified installer and taken off your quote. You never receive it as cash.
From enquiry to installation
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Step 1: Initial check
Confirm the basics: you own the property, it is in England and Wales, and oil is the main heating. Gather an EPC if you have one, and a recent oil receipt.
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Step 2: Survey and heat-loss calculation
An MCS-certified installer visits, measures each room, and looks at the tank, the boiler, the cylinder space, the electrics and where the outdoor unit could go.
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Step 3: Design and quote
The quote should list the heat pump, cylinder, radiator changes, oil boiler removal and tank arrangements. By law it must show the total cost before the grant, the value of the grant, what you pay after the grant is deducted.
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Step 4: Grant application
The installer applies. Ofgem contacts you to confirm the details, and you have 14 days to respond.
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Step 5: Run the oil down
While the application is processed, order smaller oil top-ups so there is little left to remove on installation day.
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Step 6: Installation and commissioning
The oil boiler comes out, the heat pump and cylinder go in, radiators are changed where needed, and the system is set up and tested.
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Step 7: Handover and tank removal
You are shown the controls. The tank is emptied and removed or made safe, as agreed in the quote.
Common issues in oil-heated homes
- Solid walls and older construction. Common in rural houses. It raises heat loss, which the survey accounts for, but does not rule a heat pump out.
- No cylinder space. Usually where an oil combi is fitted. Solvable in most homes, but it needs thinking about early.
- Undersized radiators. Especially in rooms that were always a little cool on oil.
- A capped gas meter at the property. It changes which grant value applies, not whether a heat pump can be installed.
- Electricity supply. The installer checks the incoming supply can carry the heat pump and, where needed, notifies the network operator.
- Secondary heating. Stoves, open fires or electric heaters in some rooms. Mention them at the survey.
Checking first costs nothing
The questions that settle most cases are simple: do you own the property, is it in England and Wales, and is there any gas meter at the address, even a capped one? If the answers look right, the survey does the rest.
Check your property
Tell us your home is oil-heated and whether you own it. We will take you to our eligibility check with those answers filled in. It is free, and nothing is sent until you choose to send it.
