For most people who drive a lot in a petrol car, CNG lowers the cost of every kilometre. The saving depends on how much you drive and on the fuel prices at the time. Prices change, so use your own numbers.
CNG also has trade-offs: some boot space, a slight change in pickup, and the need to find CNG stations. This page sets out both sides.
| Feature | CNG (bi-fuel) | Petrol |
|---|---|---|
| Running cost per km | Usually lower. The gap depends on current CNG and petrol prices | Higher per km |
| Upfront cost | One-time cost of the kit, tank and fitting | None |
| Pickup and power | A slight drop on gas, less with a good sequential kit | Full factory performance |
| Boot space | The tank takes some space | Full boot |
| Refuelling | Only at CNG stations, and the tank is filled at high pressure | Petrol pumps everywhere |
| Range | CNG range plus your petrol tank as backup | Petrol tank range |
| Upkeep | Kit service and periodic cylinder testing | Regular car servicing |
| Emissions | Generally lower carbon monoxide and particulates | Higher |
Use your monthly distance, your car's mileage on petrol and on CNG, and today's prices:
Cost per month = distance in km ÷ mileage × price per litre (petrol) or per kg (CNG)
Saving per month = petrol cost − CNG cost. Kit cost ÷ monthly saving = months to pay back.
Or let our calculator do it: Open the savings calculator
Share your car model and how you drive. We will suggest the right kit and tank and give you a clear quote.