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Is a heat pump cheaper to run than oil? Usually — but this one deserves honest arithmetic
Oil is the closest-run fuel comparison in heat pump economics — close enough that design quality genuinely decides the winner. No cheerleading here: the full kWh-for-kWh sums, the break-even SCOP, and the factors that tip an oil household clearly into savings.
- 11 min read
- Updated July 2026
- By Phil · Heat Loss Hub
QUICK ANSWER
Usually, yes — but by a margin that depends on design quality and oil prices. At mid-2026 prices, useful heat from an oil boiler costs roughly 8.5–10p per kWh; a heat pump beats that at any SCOP above roughly 3.0 on a standard tariff, and above roughly 2.4 on a heat pump tariff. A well-designed system achieving SCOP 3.8–4.3 typically undercuts oil by 20–40% — while a poor SCOP-2.8 installation can lose to a cheap oil year. Design isn’t a detail in this comparison; it is the comparison.
Oil vs heat pump, per useful kWh
Heating oil (kerosene) contains about 10.35 kWh per litre. A modern condensing oil boiler runs at up to ~90% seasonal efficiency when well maintained; many older units in the field manage 80–85%. That yields roughly 8.5–9 kWh of useful heat per litre.
COST PER USEFUL KWH — OIL VS HEAT PUMP, ILLUSTRATIVE MID-2026 PRICES
| System | Fuel price | Efficiency | Cost per useful kWh | 14,000 kWh/yr heat costs |
|---|---|---|---|---|
| Oil boiler — cheap oil year | 68p/litre | 88% | ≈ 7.5p | ≈ £1,046 |
| Oil boiler — typical | 78p/litre | 85% | ≈ 8.9p | ≈ £1,242 |
| Oil boiler — spike year / older boiler | 95p/litre | 82% | ≈ 11.2p | ≈ £1,567 |
| Heat pump — SCOP 3.0 (mediocre design) | 26p/kWh | 300% | ≈ 8.7p | ≈ £1,213 |
| Heat pump — SCOP 4.0 (good design) | 26p/kWh | 400% | ≈ 6.5p | ≈ £910 |
| Heat pump — SCOP 4.0 + HP tariff | ≈ 21p/kWh | 400% | ≈ 5.3p | ≈ £735 |
Oil prices are volatile — the same house can see its heating cost swing ±30% between years, which is precisely the exposure that pushed the government to uplift the grant for oil homes. Electricity prices are illustrative July 2026 standard rates. Method over conclusions: insert your own invoice numbers.
The break-even SCOP — one number to remember
Break-even SCOP = electricity price ÷ oil’s cost per useful kWh. At 26p electricity and 8.9p oil heat: 26 ÷ 8.9 ≈ 2.9. On a 21p heat pump tariff: ≈ 2.4.
Any properly designed system should clear 2.9 with room to spare — our retrofit designs project between 3.5 and 4.5 depending on the building and flow temperature. But note how close a bad installation sails to the line: park the flow temperature at 55 °C, skip weather compensation and oversize the unit, and SCOP slides toward 2.8–3.0 — where a cheap oil year wins. This is why oil households, more than anyone, should insist on seeing the design maths before signing. It’s also why we publish guides like Why are heat pump quotes so different?
A worked example: an oil farmhouse, measured
FROM THE DESIGN DESK
A stone farmhouse near Harrogate burning 2,400 litres a year (≈ 24,800 kWh energy, ≈ 21,100 kWh useful heat at 85%). Typical year at 78p/litre: ≈ £1,870. Spike years had touched £2,300.
Measured heat loss 11.6 kW at −4.4 °C. Design: 12 kW R290 unit, 50 °C flow, six radiator upgrades, loft and draught work bringing demand down ~8%. Projected SCOP 3.6 → 19,400 kWh heat ÷ 3.6 ≈ 5,390 kWh electricity ≈ £1,400 at 26p, ≈ £1,130 on a HP tariff. Saving: £450–£750 a year against typical oil — plus freedom from the tank, the smell, and the price roulette. The £9,000 grant covered a large slice of the installation.
What swings the comparison — both ways
- Toward the heat pump: older oil boilers (real-world efficiency in the low 80s), oil price spikes, heat pump tariffs, any solar PV, radiator headroom that allows 45–48 °C design, and the simple fact that AGA-adjacent oil pricing has no cap and no ceiling.
- Toward oil: a nearly new condensing oil boiler, unusually cheap fixed oil contracts, homes where emitter constraints genuinely force 55 °C+ design, and installations bought on price with no design behind them.
One more asymmetry worth naming: an oil boiler’s economics get worse with age; a heat pump’s stay put. And every future fuel-duty, carbon-pricing or supply shock lands on one side of this ledger only.
DESIGNER'S INSIGHT
“Oil clients get my most conservative projections on purpose. If I tell a family they’ll save £600 and they save £750, we’re friends for life; the other way round and I’ve joined the industry’s credibility problem. The oil comparison is winnable — we win it routinely — but it’s won at the design desk, at 45 degrees, not in a brochure at 55.”
Phil
Founder & Lead Designer, Heat Loss Hub
The £9,000 grant: oil homes included
The Boiler Upgrade Scheme uplift announced in April 2026 raises the grant from £7,500 to £9,000 for homes replacing oil or LPG heating in England and Wales, with applications expected to open in July 2026. The government’s stated reasoning: oil households sit outside the price cap and bore the brunt of recent supply-shock pricing. Your MCS installer claims the grant and handles all paperwork — full detail in our BUS uplift blog post.
Our honest verdict
If your oil boiler is past its prime, your radiators have any headroom, and you can access the £9,000 grant: the heat pump wins on running cost, resilience and total cost of ownership for the great majority of oil homes — provided the system is designed from a measured heat loss and run at an honest flow temperature.
If someone quotes you a heat pump without a room-by-room calculation, in this comparison specifically, they are gambling with your break-even. Get the measurement first, or have the quotes you already hold independently reviewed — the review costs a fraction of a single winter’s oil.
Frequently asked questions
With an efficient boiler mid-life, the running-cost gap is real but smaller, so many households sensibly plan rather than rush: get the design done now, do the cheap fabric work, and install at a moment that suits you (or when the £9,000 window and your boiler’s first major repair coincide). Owning the design means the eventual switch takes weeks, not panicked days.
Hybrids have a narrow honest niche where emitters can’t be upgraded and design temperatures are brutal, but they keep the tank, the service contract and the volatility — and BUS doesn’t fund them. In most oil homes a right-sized full heat pump beats a hybrid on lifetime cost and simplicity.
Usually — most domestic units draw 2–4 kW peak, similar to an electric shower’s territory. Single-phase rural supplies with existing high loads are checked at survey, and DNO applications are routine where needed. It belongs on the plan, not in the surprises column.
Decommissioning is straightforward: remaining oil can often be sold or transferred, tanks removed or repurposed, and OFTEC rules cover the details. We flag tank logistics in the design notes so it’s costed, not discovered.
Yes — the design is checked at your location’s design temperature (−4 °C or lower on the higher ground we cover), with output verified from manufacturer cold-climate data, not brochure conditions. Oil’s real winter advantage was never physics; it was familiarity.
CONTENTS
OIL HOUSEHOLD?
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THE CLOSEST COMPARISON, DONE RIGHT
Beat oil with design, not optimism
Send us your annual oil consumption and property details. We’ll reply by email with an honest first assessment — including the break-even arithmetic for your exact situation.