Home › Guides › EV vs Petrol Cost
EV vs Petrol: The Per-Kilometer Math
Auto · 6 min read · Last updated September 2026
The formula (both sides)
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
| Factor | Effect on the comparison |
|---|---|
| Purchase premium | EVs often cost more upfront — part of the 82,000 saving repays that gap |
| Charging access | Home charging at domestic rates is the cheap case; public fast charging can cost 2–3× more per kWh |
| Maintenance | EVs cut oil changes and brake wear; tyres and insurance are comparable |
| Battery & resale | Degradation uncertainty affects resale value both ways |
| Annual distance | The 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
Worked example: EV Charging Cost at its default inputs
This is the answer EV Charging Cost gives before you touch anything — the defaults as shipped, computed live rather than copied from a sample.
| Input | Default |
|---|---|
| Battery (kWh) | 60 |
| Current % | 20 |
| Target % | 90 |
| Rate ($/kWh) | 0.15 |
Result: $6.30
What Battery (kWh) does to the answer
Same calculator, same fields, one change: battery (kwh).
| Battery (kWh) | Result |
|---|---|
| 30 | $3.15 |
| 60 | $6.30 |
| 90 | $9.45 |
If the rows barely differ, battery (kwh) is not your lever — change a different input. If they swing widely, get that number right before trusting the total.
Related guides
Compare ownership, not sticker price
An electric car usually costs more to buy and less to run. The comparison only means something when both sides include purchase price or finance cost, insurance, servicing, tyres, fuel or electricity, and resale value at the point you would sell.
Depreciation is the largest single line for most new cars and the one people leave out. If resale values in your market are uncertain for one of the two, widen the range rather than picking the number that favours your preferred answer.
Electricity tariff is the EV mileage
Running cost depends on consumption (kWh per 100 km, typically 15-20 for a car), the tariff you actually pay, and how much charging happens at home. Home charging on a low domestic slab is dramatically cheaper than public fast charging on a per-unit basis.
If your tariff has slabs, the marginal unit matters, not the average. Adding an EV can push a household into a higher slab, which quietly raises the cost of the last units — include that if your usage is already near a threshold.
Where petrol still wins
Long-distance routes with sparse charging, very high annual mileage on motorways, and markets where resale or battery support is uncertain all favour the combustion car today. So does a household that cannot charge at home and relies on public infrastructure.
The break-even is usually annual distance: below a threshold, the higher purchase price never gets repaid. Above it, running cost dominates. That threshold is what the comparison should produce, not a single verdict.
Battery health is a slow-moving input
Capacity loss of roughly 1-2% a year is normal, faster with frequent fast charging and extreme heat. It affects range long before it affects usability, and it affects resale value more than it affects daily driving.
Warranty terms (often 8 years to 70% capacity) are worth reading before comparing two used EVs. Two cars at the same price with different remaining warranty are not the same purchase.
Home charging equipment is a cost too, and installation can be significant if the parking space is far from the meter. Put it in the first year of the comparison rather than treating it as infrastructure that arrives for free.
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.
Last updated