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Heat pump running costs vs oil in a Devon home come down to one number that comparison articles tend to skip: the electricity tariff you end up on. Get that right and the case against oil is usually strong. Stay on a standard variable rate out of habit and the gap can narrow to not much at all. Both answers come from the same set of figures, applied to two different households.
Key Takeaways
- Running costs turn on your electricity tariff more than on the heat pump itself, so no single UK-wide answer fits every home.
- Heating oil and LPG sit outside the Ofgem price cap, so off-grid Devon homes carry price swings that capped mains gas customers do not.
- Nesta’s April 2026 research puts a typical saving for a medium-sized home leaving oil at just over £650 a year, at that month’s prices.
- A typical UK air source heat pump averages a SCOP of around 3: roughly three units of heat for every unit of electricity across a season.
- Off-gas-grid homes replacing oil or LPG can qualify for £9,000 through the Boiler Upgrade Scheme, on applications made up to 31 March 2027.
- The figure worth trusting is one worked out for your own property, your tariff and what you pay for oil now.
This guide works through the mechanics behind that: why oil sits outside the price cap and what that exposure means for a tank in the garden, what SCOP tells you about a heat pump’s own efficiency, why the tariff changes the sums more than the equipment does, and one sourced running-cost figure with its conditions spelled out. You will find no invented percentage here, and no single verdict for every Devon property.
Why Heat Pump Running Costs vs Oil Doesn’t Have One Answer
Two households on the same street, both switching from oil to a heat pump in the same year, can end up with genuinely different verdicts. One moves to a heat-pump-specific electricity tariff and schedules the heating around it. The other stays on a standard variable rate out of habit. The heat pump itself might be identical, and the running-cost outcome usually isn’t.
Same street, same heat pump, two verdicts (illustration)
Anyone quoting a single UK-wide saving percentage has skipped past all three.
The next sections take each variable in turn: the oil side first, since that is usually the more urgent question for someone reading this, then the heat pump’s own numbers, then the tariff, then what a properly sourced running-cost figure looks like.
Oil’s Real Problem Isn’t the Price, It’s the Swings
Heating oil has no single national price the way mains gas or electricity does. It is bought from a merchant at whatever the market is doing on the day of delivery, in one lump sum, with nothing capping how far that price can move between one winter and the next. A homeowner topping up the tank in October has no real way of knowing what the same fill will cost in January.
Inside the price cap and outside it (illustration, no real prices)
The lines show the shape of each exposure only. Heating oil and LPG sit completely outside the Ofgem energy price cap.
Off-grid households absorb price swings that mains gas customers on a capped tariff never carry. For a Devon property still on oil, that exposure is usually the running-cost story before any heat pump number gets involved: how far the cost of a fill can move, as well as what it costs today. Our guide to replacing an oil boiler with a heat pump in Devon covers what changes on the day the heat pump takes over from oil.
What SCOP Actually Means for a Heat Pump’s Running Costs
Illustration: an air-to-water heat pump opened up, showing the finned coil that gathers heat from the outside air and the compressor that runs on electricity.
A heat pump moves heat that is already in the outside air into the house, using electricity to run the process, and burns no fuel to do it. How much heat it moves for each unit of electricity is what efficiency means for a heat pump, and the industry-standard measure of it is SCOP.
One reading against a whole season
Roughly three units of heat delivered for every one unit of electricity used, averaged across the year.
Industry data reported by the Energy Saving Trust. A UK-wide average, with no promise for any one installation.Those three things are exactly what a room-by-room heat loss survey establishes for a given property, instead of assuming them.
The Electricity Tariff That Changes the Whole Comparison
A heat pump on a standard household tariff and the same heat pump on a tariff built for heat pumps can post clearly different running costs, without a single component underneath them changing. The unit does the same job either way. What differs is when the electricity it draws gets charged at the expensive rate and when it doesn’t.
Three tariff structures across one day (illustration)
Each ring shows the shape of a structure only, with midnight at the top. The windows are not drawn to any supplier’s actual times, and Cosy Octopus is named as one example on the market when this guide was written.
Which tariff suits a household depends on how the heating gets scheduled day to day, more than on which supplier looks cheapest on paper. That is no reason to pick one blind. We talk through the tariff question at the free home assessment, because recommending a heat pump without mentioning what it costs to run on the tariff you are actually on is only half the answer.
What the Honest Numbers Actually Say
Heat pump savings figures online tend to arrive in one of two forms: a marketing number with no source attached, or a horror story with no context. Here is one figure with a named source and its conditions spelled out.
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Dated to April 2026 Based on the energy price cap level and oil prices as they stood that month, when Nesta ran the research.
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Grant assumed The figure assumes the household claims the enhanced Boiler Upgrade Scheme grant on the upfront cost.
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Moves with oil As oil prices move, that gap moves with them, which is the volatility point from earlier in this guide.
For property owners in England and Wales. It lowers what a system costs to install, and what it costs to run is a separate sum.
Eligibility depends on the property and your circumstances, so not every home qualifies, and we check yours at the free home assessment before anything is promised. Our guide to the £9,000 rate for oil and LPG homes sets out the rules, and the air source heat pump cost guide covers the installation side of the sum in full.
Getting a Real Running-Cost Number for Your Own Home
Illustration: heat pumps in a range of sizes beside a cylinder and a wall thermostat. The heat loss survey decides which size a house needs.
Every figure in this guide, Nesta’s £650, the SCOP average of 3 and the Cosy Octopus tariff structure, is a UK-wide or industry number. None of them is your number, and each one has a counterpart that changes from one Devon address to the next.
The figures in this guide, and what replaces each for your house
Full detail on how the design and installation work sits on our air source heat pump installation page.
Frequently Asked Questions
Often, but not automatically. It depends mainly on the electricity tariff you move to and the price of oil at the time, more than on the heat pump alone. Nesta’s figures, from April 2026, put a typical saving for a medium-sized home at just over £650 a year based on prices at that time, which is no guarantee for every property.
Book my free home assessmentSCOP, the Seasonal Coefficient of Performance, measures a heat pump’s efficiency averaged across a whole heating season rather than at one outdoor temperature. A typical UK air source heat pump runs at around 3, meaning roughly three units of heat for every unit of electricity used.
Book my free home assessmentNot strictly, but it usually helps. Tariffs built for heat pumps, such as Cosy Octopus, offer cheaper rates during set windows through the day, which can lower running costs compared with a standard variable rate for the same heat pump.
Book my free home assessmentThe Ofgem price cap only applies to standard variable mains gas and electricity tariffs. Heating oil and LPG are priced by the open fuel market and aren’t covered by it at all, which is why off-grid homes in Devon see bigger price swings than capped mains gas customers.
Book my free home assessmentIt depends on your property, tariff and current oil price, so we won’t quote a blanket figure. Nesta’s research, from April 2026, suggests a typical saving for a medium-sized home of just over £650 a year based on prices at that time. Separately, off-gas-grid oil and LPG homes in England and Wales can qualify for a £9,000 Boiler Upgrade Scheme grant towards installation, on applications made by 31 March 2027.
Book my free home assessmentBook a free home assessment. James checks the property, the current system and grant eligibility, then talks through the tariff question honestly before any figure gets quoted for your house specifically.
Book my free home assessmentGet a Real Number for Your Own Property
No single figure, ours or anyone else’s, tells you what switching from oil costs to run in your house. A free home assessment gets you a number worked out for your property: what heats it now, the tariff you would move to, and whether the grant applies.
Book my free home assessmentPrefer to talk it through first? Ring 01395 202030. James answers, and he is the person who will price the job.
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