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EV vs Petrol: The Per-Kilometer Math

Auto · 6 min read · Last updated September 2026

Quick answer: Running cost per km = energy per km × energy price. An EV using 15 kWh/100km at 8/unit costs 1.20/km; a petrol car at 15 km/L and 100/L costs 6.67/km. Over 15,000 km a year: 18,000 vs 100,000 — an 82,000 annual running-cost gap before purchase price and depreciation.

The formula (both sides)

EV: cost/km = kWh per km × electricity price
Petrol: cost/km = fuel price ÷ efficiency

Worked example: EV at 15 kWh/100 km (0.15 kWh/km) × 8/unit = 1.20/km. Petrol at 15 km/L and 100/L = 100 ÷ 15 = 6.67/km. At 15,000 km/year: EV 18,000 vs petrol 100,000 → 82,000/year saved on energy alone.

What the simple math leaves out

FactorEffect on the comparison
Purchase premiumEVs often cost more upfront — part of the 82,000 saving repays that gap
Charging accessHome charging at domestic rates is the cheap case; public fast charging can cost 2–3× more per kWh
MaintenanceEVs cut oil changes and brake wear; tyres and insurance are comparable
Battery & resaleDegradation uncertainty affects resale value both ways
Annual distanceThe saving scales linearly — 5,000 km/yr shrinks it to ~27,000

The honest bottom line

High-mileage drivers with home charging see the fastest payback on the purchase premium; low-mileage drivers relying on public fast charging may never close it. Compute your own case with the EV Charging Cost and Fuel Cost calculators — and the EV vs Petrol comparison puts both sides in one output.

Try the calculators

Frequently asked questions

Is an EV cheaper to run than a petrol car?

On energy alone, almost always: 1.20/km at domestic charging rates vs 6.67/km for a 15 km/L petrol car at 100/L. Whether the total wins depends on purchase premium, charging access and how many km you drive.

How do I calculate EV cost per km?

Multiply energy use per km by your electricity price. 15 kWh/100 km = 0.15 kWh/km; at 8 per unit that is 1.20 per km.

How much can I save per year with an EV?

At 15,000 km/year in the worked example: 18,000 charging vs 100,000 in petrol — 82,000. Scale linearly with your distance and local prices.

Does fast charging change the math?

Yes — public DC fast charging typically costs 2–3× domestic rates per kWh, pushing EV cost/km toward 2.5–3.5. Frequent fast-charge users should model that rate, not the home rate.