Your oil boiler is on its way out. The real question is which purchase is better for this house, this year: another boiler or a heat pump. The table below compares them on ten factors, with a winner per row. Figures assume a typical 4-bed rural home at 2026 prices. Deeper numbers live in the running costs guide and cost guide.
The Decision Table
| Factor | New oil boiler | Air source heat pump | Winner |
|---|---|---|---|
| Upfront cost (2026) | £4,000–£6,000, no grant | £10,000–£14,000 minus £9,000 = £1,000–£5,000 | Heat pump* |
| Running cost / yr | ~£1,550–£1,750 | ~£1,130 on a heat pump tariff | Heat pump |
| Price stability | Uncapped; moves with world markets | Price-capped electricity, fixable tariffs | Heat pump |
| Lifespan | 10–15 yrs | 15–20 yrs | Heat pump |
| Annual maintenance | £100–£180 + burner parts with age | £150–£250, fewer wearing parts | Draw |
| Fuel logistics | Tank, deliveries, level-watching, theft/leak risk | None — it's wired in | Heat pump |
| Space | Boiler + tank and its clearance zone | Outdoor unit + cylinder; garden back from the tank | Heat pump |
| Installation disruption | 1 day, like-for-like | 2–3 days incl. radiator swaps | Oil boiler |
| Very hot fast radiators | 70 °C blast on demand | Lower, steadier temperatures by design | Oil boiler (habit); comfort is a draw run properly |
| Carbon per kWh of heat | ~300g CO₂ | ~40–60g and falling with the grid | Heat pump |
When Does the Oil Boiler Honestly Win?
Three cases: your boiler has died mid-winter and the house can't bridge a few weeks; you're selling within two or three years; or the house has extreme heat loss and you'll accept no radiator or fabric changes at all. Outside those, the 2026 numbers favour the heat pump.
Your boiler dies in January and the house can't wait — a like-for-like swap is back on in a day, and cold houses make bad five-year decisions; even then, ask whether a fortnight's bridging with electric heaters is worth £1,500 of extra grant and a decade of lower bills. You're selling within two or three years — you may not hold the house long enough to collect the running-cost savings, though a granted heat pump and better EPC increasingly reads as a selling point rather than a cost. The house has extreme heat loss and no appetite for any fabric work or radiator changes — a heat pump will still heat it, but the economics narrow; get the survey numbers before deciding either way (see old houses guide).
When Does the Heat Pump Win?
Most other cases from 21 July 2026: a working-but-ageing boiler you can sequence around the £9,000 window, an annual oil spend over £1,500, or any LPG home. A net install cost of £1,000–£5,000 pays back in 3–8 years on fuel alone.
If your boiler is limping rather than dead, the sequencing is free money: survey now, apply on day one, install before winter — the oil boiler replacement page walks the whole path, tank removal included. If your annual oil spend is £1,500+, the running-cost gap alone repays the net install cost in 3–8 years, inside the warranty window let alone the unit's life. And if you're on LPG rather than oil, every number above improves in the heat pump's favour by another £1,000 a year. The one precondition that actually matters: a proper heat loss survey and a design SCOP you can hold your installer to — a badly designed heat pump loses to a well-serviced boiler, and no table can fix that.
What About a Hybrid — Keep the Boiler, Add a Heat Pump?
Tempting on paper, excluded in practice: the Boiler Upgrade Scheme requires full replacement, so a hybrid forfeits the entire £9,000 — you'd pay £10,000+ gross to keep a boiler a correctly sized heat pump makes redundant. Hybrids have a niche in very large, unimprovable properties bridging toward fabric work; for a normal Bucks village house they're an expensive way to hedge a risk the heat loss calculation already answers.
Head-to-Head Questions
Will a heat pump heat my water as hot as the oil boiler did?
Your cylinder stores water at 48–55 °C — the same range a well-set boiler cylinder uses, and hot enough that your shower mixes it down anyway. A weekly automatic sterilisation cycle takes the tank higher for legionella control. What changes is capacity planning, not temperature: the cylinder is sized to your household at the survey.
Is the heat pump comparison rigged by the grant? What if it ends?
Partly — that's the point of the grant, and why the window matters. At full price the heat pump's case rests on running costs and lifespan and takes a decade to pay back against oil; at £9,000 off it pays back in single digits and often beats the boiler on the day you buy it. Grants shape markets; this one is shaped in your favour until 31 March 2027.
What happens to the comparison if oil gets cheap again?
At 50p/litre — the cheap end of recent years — oil heat costs ~5.7p/kWh and roughly matches a heat pump on a good tariff, rather than losing. The difference: oil visits that price and leaves; you'd be betting a 15-year appliance on the friendliest year in a volatile decade, with no cap if the bet goes wrong.
Can I get a heat pump that just drops into my oil boiler's spot?
The indoor kit (cylinder, controls) often lands where the boiler and old tank cupboard were, but a heat pump is a system change, not a swap — the outdoor unit, radiator checks and controls are what make it work. Anyone selling a "drop-in" heat pump without a survey is selling the horror story you've read about. What a proper installation involves is on the air source heat pump page.
Settle It With Your Own Numbers
The table above is the county average; your house has exact figures. A free heat loss survey prices both futures — the granted heat pump with its projected running costs, next to what staying on oil actually costs you per year — and the decision usually makes itself. Grant eligibility is on the Boiler Upgrade Scheme hub.