The answer is determined by the building, not by the technology. A well-insulated house with generous emitters and somewhere sensible for an outdoor unit is a good heat pump candidate. A solid-wall cottage with small radiators and a stone floor is a much harder proposition, and pretending otherwise helps nobody.
Why this question matters so much here
Norfolk is one of the least connected counties in Great Britain for mains gas, which means a very large number of households face this decision rather than simply replacing a gas boiler.
Those are DESNZ estimates for 2024. The full picture, district by district, is on the Norfolk off-grid heating map.
The physics, briefly, because it determines everything
An oil boiler burns fuel and produces heat at whatever temperature you ask for. Its efficiency is roughly constant across its operating range and largely independent of the weather.
A heat pump moves heat rather than making it, extracting energy from outside air and upgrading it. Its efficiency – expressed as a coefficient of performance – depends strongly on two things: how cold it is outside, and how hot you ask the water to be. The bigger the temperature lift, the harder it works and the lower the efficiency.
That second factor is the whole story, and it is why the building matters more than the appliance.
A heat pump running at a low flow temperature can be genuinely efficient. The same heat pump asked to produce high-temperature water to feed small radiators in an uninsulated house will be far less efficient and expensive to run. Whether your building can be heated at a low flow temperature is the question that decides this, and it is answered by a heat loss survey, not by a brochure.
What makes a good heat pump candidate
| Good candidate | Harder proposition |
|---|---|
| Cavity walls, insulated | Solid walls, uninsulated |
| Good loft insulation and draught-proofing | Draughty, with an uninsulated roof |
| Double or triple glazing throughout | Single glazing, or original windows in a listed building |
| Generously sized radiators, or underfloor heating | Small panel radiators sized for a high flow temperature |
| A clear outdoor position away from neighbours | Terraced, or a narrow gap to a neighbour’s window |
| Space for a larger hot water cylinder | No room, or a combi with no cylinder at all |
| Modest hot water demand, or a well-designed cylinder | Very high simultaneous hot water demand |
| Owner intending to stay long enough to benefit | Short remaining tenure |
A great deal of Norfolk’s off-grid housing sits in the right-hand column. That is not a reason never to fit a heat pump – it is a reason to be honest about what would have to change first, and what it would cost.
What a heat pump conversion actually involves
This is where the honest conversation matters, because the appliance is frequently the smaller part of the project.
- A proper room-by-room heat loss survey. Not optional and not a formality – it determines the heat pump size and every radiator in the house.
- Emitter upgrades. Most existing radiators are sized for a high flow temperature. At heat pump temperatures they deliver considerably less, so many need to be larger. This is usually the largest single item after the appliance.
- A cylinder. Heat pumps need a cylinder with a much larger coil surface area than a boiler cylinder, because they are transferring heat at a lower temperature. An existing cylinder is very rarely suitable.
- Pipework. Lower flow temperatures mean higher flow rates for the same heat, and some existing pipework is undersized for that.
- Fabric improvements, where the heat loss is high enough that the alternative is an oversized, expensive-to-run system.
- Electrical supply, which may need attention.
- Outdoor unit siting, with noise and permitted development considered.
Anyone quoting a heat pump without a heat loss survey is quoting for an appliance rather than for a heating system, and the result will disappoint.
The honest trade-offs
Where a heat pump genuinely wins
- In a well-insulated building where a low flow temperature actually heats the house.
- Where underfloor heating already exists, which is close to ideal.
- Where carbon reduction matters to the owner as a goal in itself.
- Where grant support materially changes the capital cost.
- Where there is also solar generation to use.
- It provides cooling in some configurations, which oil never will.
- No fuel deliveries, no tank, no run-dry, no tank replacement in fifteen years.
Where oil still makes more sense
- A poorly insulated solid-wall building where the fabric work is not happening.
- Where there is genuinely nowhere acceptable to put an outdoor unit.
- Where very high flow temperatures are needed for the existing emitters and changing them is impractical – a listed interior, for instance.
- Where the capital available does not stretch to doing it properly, and a half-done heat pump conversion is worse than a good oil boiler.
- Where the household needs large volumes of hot water quickly.
We will not tell you an oil boiler is your only option when it is not, and we will not sell you a heat pump into a building that will be cold and expensive to run. Both of those happen, and both damage people’s trust in the trade.
A middle path worth knowing about
There is a third option that gets discussed less than it should: improve the system now so that a heat pump becomes viable later.
If you are replacing an oil boiler today, you can specify the replacement system for a lower flow temperature – larger radiators, a properly cleaned and balanced system, weather compensation – and run the oil boiler at that lower temperature. It is more efficient immediately, because a condensing oil boiler condenses better at low return temperatures. And it leaves the house ready for a heat pump whenever the economics or the fabric change, with the expensive emitter work already done.
That is a genuinely sensible position for a lot of Norfolk properties, and it avoids both the trap of locking the house into high-temperature heating for another fifteen years, and the trap of fitting a heat pump into a building that is not ready for one.
We do not currently advertise heat pump installation, because the certification that gates the customer’s grant eligibility is not recorded on file – and we will not advertise work whose credential we cannot evidence. That does not stop us giving you an honest assessment of whether your building suits one, and it is worth having that assessment before you commission anybody.
Replacing an oil boiler? Ask for the heat loss survey whichever technology you end up with. It changes the radiators either way.
Questions we get asked about this
Is a heat pump cheaper to run than oil?
It depends on your building and on the relative prices of electricity and heating oil, both of which move. In a well-insulated house running at a low flow temperature, it can be. In a poorly insulated house needing high flow temperatures, it frequently is not. The building determines it.
Can I just swap the oil boiler for a heat pump?
Almost never as a straight swap. The radiators, the cylinder and often some pipework need to change, because a heat pump delivers heat at a much lower temperature than a boiler. A like-for-like swap is the most common cause of a heat pump that disappoints.
Will my radiators be big enough?
Usually some will not be. Radiator output falls substantially at heat pump flow temperatures compared with boiler temperatures, so the heat loss survey will identify which rooms need larger emitters.
What about grants?
Grant support for heat pumps exists and it materially affects the capital cost, with eligibility conditions attached – including installation by a certified installer. Check the current scheme rules directly, as the terms change.
Are heat pumps noisy?
The outdoor unit produces a continuous mechanical sound. It is not loud, but it runs for long periods and it is outside. Siting matters, particularly relative to neighbours and bedroom windows.
Should I improve insulation first?
If the choice is between spending on fabric and spending on a heat pump for a poorly insulated house, fabric first is usually the better answer. It reduces the heat pump you need, improves comfort immediately, and it works whatever heating you end up with.
Sources
- Department for Energy Security and Net Zero, Subnational estimates of properties not connected to the gas network (published 18 December 2025, 2024 data). Contains public sector information licensed under the Open Government Licence v3.0.
You might also need
- Bunded or single-skin? How to tell which tank you are allowed
- Buying heating oil: order size, timing and tank management
- Eight signs an oil tank is near the end of its life
- Frozen condensate pipes: why it happens and how to stop it recurring
- Grant, Firebird, Warmflow, Worcester Danesmoor and Mistral, compared honestly
- Internal, external or boiler house: where an oil boiler should go
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.