Most running-cost claims fail a simple test: they compare a best-case heat pump with a worst-case boiler, or the reverse. This guide uses one method for every fuel. We price the heat delivered into the house, after appliance efficiency, at early-2026 prices. Then we multiply by a realistic annual heat demand. You can rerun the method with your own bills.
What Do COP and SCOP Actually Mean?
COP is the ratio of heat out to electricity in at one moment: a COP of 3.5 means 1 kWh of electricity delivers 3.5 kWh of heat. SCOP is the same ratio averaged over a whole year's weather. A well-designed 2026 system here achieves a SCOP of 3.5–4.0.
A heat pump moves heat rather than making it, which is how it beats 100% efficiency. COP runs high in mild weather and drops on frosty mornings; SCOP averages a full year of real weather, which is why it's the figure your bills follow. A poorly designed system running hot radiators at full tilt might manage 2.5 — roughly £400 a year worse than a 3.5 system on a typical house. When you compare quotes, compare the design SCOP: it's the number your installer is accountable for, and it's on the MCS paperwork.
How Do the Fuels Compare, Like for Like?
Boilers waste some fuel up the flue (an oil or gas boiler in good order delivers about 85% of the energy it burns; LPG similar), electric heaters deliver 100% but at the full electricity price, and a heat pump multiplies its input by the SCOP. Applying that to early-2026 prices:
| Heating system | Per kWh of heat | Per year |
|---|---|---|
| Heat pump — heat pump tariff | ~5.1p | ~£1,030 |
| Mains gas boiler | ~7.3p | ~£1,460 |
| Heat pump — standard tariff | ~7.0p | ~£1,400 |
| Oil boiler | ~7.0–8.0p | ~£1,550 |
| LPG boiler | ~11.5p | ~£2,300 |
| Storage heaters (Economy 7) | ~15–17p | ~£3,200 |
| Direct electric (panels, fan heaters) | ~24.5p | ~£4,900 |
LPG figure assumes 6.6 kWh/L. Oil and LPG prices are uncapped and move with markets — the ranges here are winter 2025/26 averages for the South East.
Reading it honestly: against oil, a heat pump on a standard tariff roughly breaks even and wins by £400–£600/yr on a heat pump tariff — plus oil's hidden costs (deliveries, tank maintenance, price spikes in cold snaps) that never appear on a unit-price table. Against LPG, the heat pump wins heavily on any tariff — typically £1,000–£1,300/yr. Against mains gas, it's close: a good SCOP on a heat pump tariff beats gas by a few hundred pounds; a mediocre SCOP on a standard tariff loses. Against electric heating of any kind, it's not a contest — the heat pump cuts the bill by two-thirds or more. That's why our busiest pages are oil boiler replacement and storage-heater conversions, and why we'll tell a gas-heated household the truth: switch for the right reasons, not for guaranteed savings.
How Do I Estimate My Own Annual Heat Demand?
You don't need a survey to get close — your current bills already contain the answer. On oil: annual litres × 10.35 × 0.85 ≈ your heat demand in kWh (so 2,000 L ≈ 17,600 kWh). On LPG: litres × 6.6 × 0.85. On mains gas: the kWh on your bill × 0.85, minus a little for cooking.
On electric heating: your winter-months usage above the summer baseline, near enough as-is. Typical results: 10,000–14,000 kWh for a well-insulated 3-bed, 18,000–24,000 kWh for a 4-bed detached, 25,000 kWh+ for a large or draughty rural house. Divide by the SCOP, multiply by your electricity rate, and you've reproduced this guide's method with your own numbers. Hot water adds roughly 2,500–3,500 kWh a year for a family of four and is already inside these bill-derived figures.
And if the decision you're actually weighing is a heat pump versus a straight replacement oil boiler, running costs are only one row of the table: our heat pump vs oil boiler head-to-head scores the whole choice — upfront cost after the grant, lifespan, maintenance, fuel logistics and price stability — across ten factors with a winner per row.
What Is a Heat Pump Tariff, and How Much Does It Save?
A heat pump tariff is a discounted electricity rate for heat pump owners — several major suppliers now sell one, either a flat 15–20p/kWh against the 24.5p standard rate (2026 figures) or cheap overnight windows a hot water cylinder can exploit. On the 20,000 kWh house above it saves roughly £370 a year.
That's about the same as the entire oil-vs-heat-pump margin. Two practical notes: most require a smart meter, and some bundle in your whole household's electricity, so the savings spill over into everything else you run. We set new systems up with tariff guidance at handover because a good install on a bad tariff leaves money on the table every month.
What Makes One Heat Pump Cheaper to Run Than Another?
Four things, all decided before installation day: flow temperature (every degree lower is roughly 2–3% more efficient), weather compensation, correct system sizing, and your house's insulation. Get the first three right and the same house runs several hundred pounds a year cheaper than it would on a careless installation.
In detail: big enough radiators let the system run at 40 °C instead of 55 °C. Weather compensation trims flow temperature against outdoor conditions rather than holding a fixed setpoint — standard on our installs and worth several hundred kWh a year. An oversized unit short-cycles and an undersized one leans on its backup immersion; both trace back to whether anyone did a real heat loss calculation (the air source heat pump page explains how ours works). And insulation sets the size of the bill for any heating system — a heat pump multiplies whatever your fabric asks of it.
Running Cost Questions
Do bills spike in a cold snap like they do with oil?
Usage rises in cold weather (as with any heating), but the price doesn't — electricity is price-capped and contracted, unlike heating oil, which regularly jumps 10–20% exactly when everyone's tank runs low. The heat pump also loses some efficiency below freezing, which the SCOP already averages in. What you'll never have again is the £700 emergency top-up in January.
Do I need solar panels to make the numbers work?
No — every figure on this page assumes grid electricity only. Solar helps (especially for summer hot water) but most generation lands in the months you heat least, so treat it as a separate investment with its own maths, not a requirement.
Is it true you should leave a heat pump on all the time?
Broadly, yes — low and steady beats blast-and-cool. A heat pump runs most efficiently at low flow temperatures, gently holding the house at temperature, with a modest setback (not off) overnight. Running it like a boiler — off all day, full power at 6pm — forces high flow temperatures and costs more. It's a habit change, and we set the schedules up with you at handover.
What if electricity prices rise — am I more exposed than on oil?
Less, in two ways. A heat pump only feels a third of any electricity rise, because each kWh you buy delivers 3.5 of heat — a 10% price rise moves the annual bill by ~3% of heat cost. And electricity is the fuel governments are actively cheapening: policy levies are being shifted off electricity bills precisely to favour heat pumps. Oil moves with global markets, unhedged and uncapped, and you carry 100% of every move.
What about the £9,000 grant — does that change the running-cost picture?
It changes the payback, not the running cost. For an oil or LPG home the Boiler Upgrade Scheme covers most of the installation from 21 July 2026, so the annual saving pays back the net cost in a few years rather than a decade — details in our £9,000 grant guide and full install pricing in the cost guide.
Get These Numbers Calculated for Your House
Every figure above becomes exact after a heat loss survey: your demand, your design SCOP, your tariff options, your annual cost next to your current fuel. The survey is free and the report is yours either way — see the air source heat pump page for what's involved, or the grant hub for what the government pays towards it.