Replacing an Oil Boiler in Cornwall: Your 2026 Options
Around 55% of Cornwall homes are off the gas grid and rely on oil. When your boiler fails, you have three realistic options — and the economics have shifted significantly in favour of heat pumps in 2026.
The State of Oil Heating in Cornwall in 2026
Around 55% of Cornwall homes are off the gas grid. In rural areas — Bodmin Moor, the Roseland, West Penwith — the figure rises to 80–95%. Oil heating has dominated these properties for 40 years, but the economics are shifting decisively. Oil prices have been volatile, averaging around 75–85p per litre in 2025–26. Meanwhile, the Boiler Upgrade Scheme offers £7,500 towards an air source heat pump, and modern ASHPs achieve SCOP 3.0–3.8 in Cornwall's mild climate.
When your oil boiler fails, you have three realistic options. Here's an honest comparison.
Option 1: Like-for-Like Oil Boiler Replacement
A new oil condensing boiler from Worcester Bosch, Grant or Firebird costs £2,200–£3,500 installed in Cornwall (2026 prices). Modern A-rated condensing oil boilers run at 91–93% efficiency — significantly better than the 75–84% of 15-year-old units. Payback from efficiency gains alone is typically 3–5 years.
Pros: Lowest upfront cost, familiar system, quick installation (1–2 days), works with existing radiators and hot water cylinder at original flow temperatures.
Cons: Continued exposure to oil price volatility, oil tank maintenance requirements, future government restrictions on fossil fuel heating likely after 2030, no grant support in 2026.
Option 2: LPG Conversion
LPG (propane/butane) burns cleaner than oil and doesn't require the same tank maintenance, but it's more expensive per kWh — typically 9–11p/kWh versus 7–9p/kWh for oil in 2026. LPG conversion makes most sense where the property already has an LPG supply (holiday let complexes, farm sites) or where the oil tank needs replacement anyway.
Installed cost for LPG conversion: £2,800–£4,200 including new boiler and tank rental setup. Running costs are typically 15–25% higher than oil per kWh delivered.
We generally don't recommend fresh LPG installation in 2026 unless there's a specific property reason — the economics rarely beat either oil or heat pumps.
Option 3: Air Source Heat Pump With BUS Grant
An air source heat pump with the £7,500 BUS grant represents the most substantial shift but often the strongest 10-year economics. In Cornwall's mild climate (average annual temperature ~11°C), a modern ASHP from Mitsubishi Ecodan R290 or Vaillant Arotherm Plus achieves SCOP 3.2–3.8. This means for every £1 of electricity you spend, you get £3.20–£3.80 of heat.
Gross installed cost for a typical 3–4 bed Cornwall off-gas property: £13,000–£18,000. After the £7,500 BUS grant: £5,500–£10,500. For properties eligible for additional HEAT Cornwall or ECO4 support, the net cost can be lower still. See our guide to stacking Cornwall energy grants.
For the heat pump to work well, you need: adequate radiator surface area (ideally oversized or replaced with larger rads), or underfloor heating. Properties with existing UFH are ideal candidates. Properties with small radiators may need upgrades, adding £1,500–£3,500 to the project.
Comparing 10-Year Costs
Based on a typical 3-bed Cornwall off-gas home, annual heating demand 18,000 kWh:
| Option | Install cost (net) | Annual running cost | 10-year total |
|---|---|---|---|
| New oil boiler | £2,800 | ~£1,620 (oil @ 8p/kWh, 90% efficiency) | ~£19,000 |
| ASHP (after BUS grant) | £7,500 | ~£1,100 (electricity @ 24p/kWh, SCOP 3.5) | ~£18,500 |
| ASHP + solar panels | £12,500 | ~£700 (reduced electricity draw) | ~£19,500 |
The heat pump + solar combination breaks even at around year 12 versus a new oil boiler, but provides far greater energy independence and insulation against future oil price rises. And heat pump running costs improve as electricity grid decarbonises; oil costs are expected to remain volatile.
Practical Considerations for Each Option
Oil boiler: Check your oil tank first. A 25+ year old single-skin plastic tank often needs replacement at the same time (£600–£900 installed). Factor this into the comparison. OFTEC registration required — your installer must be OFTEC-registered to work on oil systems.
Heat pump: The BUS grant requires MCS-certified installation and a current EPC. The EPC must show the property is suitable (no requirement to have a specific rating, but the assessor must confirm suitability). We handle the grant application paperwork as part of installation. Typical lead time from survey to installation: 4–8 weeks in 2026.
Our Recommendation
For most off-gas Cornwall properties replacing a boiler in 2026, we recommend getting quotes for both a new oil boiler and an ASHP with BUS grant, then comparing total 10-year costs including any required radiator upgrades. For properties with existing UFH or large radiators, the heat pump almost always wins. For properties with small old radiators and no budget for upgrades, a new oil boiler may be the pragmatic short-term choice — but plan for heat pump conversion within the decade.
Contact us for a free survey and honest comparison for your specific Cornwall property. We install both oil boilers and heat pumps and have no incentive to push one over the other beyond what genuinely suits your home.
Need personalised advice?
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