What is LPG, and is it worth converting?
LPG (Liquefied Petroleum Gas), sold at forecourts as "autogas," typically costs around 75–85p per litre compared to 155–160p for petrol. That's a tempting gap. But LPG contains less energy per litre, so you use more of it. Conversion costs £1,000–2,500. And the forecourt network is shrinking. Here's the honest maths.
The real cost per mile comparison
LPG has a lower calorific value than petrol, roughly 6.9 kWh/litre vs 8.9 kWh/litre. This means a converted car consumes approximately 15–20% more LPG by volume to travel the same distance as on petrol. The fuel savings are still real, but smaller than the raw price difference suggests.
Even accounting for the higher consumption, LPG typically saves around 40% per mile compared to petrol at current prices. At 15,000 miles per year with an average fuel economy of 35 mpg equivalent, a typical driver could save around £800–1,000 annually.
The break-even calculation
With a mid-range conversion costing around £1,800 and annual savings of £900, the break-even point is around 2 years. That assumes consistent high mileage and the availability of LPG on your regular routes. Every vehicle, usage pattern and local fuel price is different. Run the numbers for your specific situation before committing.
The UK's LPG network has shrunk significantly as electric vehicle investment has dominated forecourt development. While there are still ~1,400 stations, they're not evenly distributed. Rural areas in particular may have long gaps between LPG pumps. Check the Autogas Live map before converting to confirm your regular routes are covered.
Is LPG right for you?
| Factor | LPG suitable? |
|---|---|
| High annual mileage (15,000+ miles) | Yes, savings add up |
| Regular motorway / long routes | Yes, better range per tank |
| Urban-only short journeys | No, break-even takes too long |
| Planning to keep car 5+ years | Yes |
| Rural area with poor LPG coverage | No, range anxiety risk |
| Car valued over £5,000 | Possibly, better conversion ROI |
For high-mileage drivers considering a major investment in alternative fuel, a secondhand EV with home charging may now offer better long-term economics than LPG, particularly as the LPG network continues to contract. Worth modelling both before deciding.