CNG vs Petrol vs EV Running Cost Comparison
Compare cost per km across fuel types, and simple payback on a conversion kit
Frequently Asked Questions
Comparing petrol, CNG, and electric running costs side by side means converting each fuel type's very different pricing (per litre for petrol/diesel, per kg for CNG, per kWh for electricity) into one common unit — cost per kilometre — since comparing raw prices per unit across fuel types tells you nothing about which is actually cheaper to drive.
Why cost-per-km is the only fair comparison basis
Each fuel type has a different price per unit and a different efficiency (distance covered per unit), so neither number alone determines which fuel is cheaper to run — a fuel that costs more per unit but delivers proportionally more distance per unit can still work out cheaper per kilometre than a cheaper-per-unit fuel with worse efficiency. This calculator normalizes all fuel types to cost per kilometre specifically so petrol, CNG, and electric (home charging) options can be ranked on the same basis, and separately estimates payback period for a CNG conversion kit — since a kit has an upfront cost that only pays for itself once accumulated fuel savings, at your actual monthly driving distance, exceed that upfront cost.
A worked example
A CNG conversion that saves a meaningful amount per kilometre compared to petrol needs a specific number of kilometres driven to fully offset the kit's upfront installation cost — a low-mileage driver takes proportionally longer to reach that breakeven point than a high-mileage driver covering the same monthly distance repeatedly, which is exactly why conversion payback depends heavily on actual usage pattern, not just the per-km savings rate alone.
How this connects to your other vehicle costs
This calculator's cost-per-km figures build directly on the same fuel-price and mileage inputs used in the Fuel Cost Calculator — if you don't have an accurate mileage figure for each fuel type option you're comparing, track it first with the Mileage Calculator rather than guessing, since an inaccurate mileage input for any one fuel type will skew that option's ranking relative to the others.
Common mistakes
Comparing fuel types using headline price-per-unit figures (petrol's price per litre against CNG's price per kg, for instance) without converting to a common cost-per-km basis first is the most common mistake — the raw per-unit prices aren't directly comparable across fuel types with different efficiencies, and only the normalized per-km figure actually answers "which is cheaper to drive."