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EV vs petrol — the 5-year math nobody finishes
Quick answer: the energy half of the comparison is genuinely lopsided. At 15,000 km/year, home-charged EV energy costs about 18,000 vs 100,000 in petrol — an 82,000/year gap. But the comparison only becomes honest when the purchase premium pays that gap back (about 4.9 years on a 400,000 premium in this example) and the numbers people never finish — charging access, insurance and depreciation — join the table.
The energy math, quickly (it's the easy part)
EV at 15 kWh/100 km and 8/unit: 0.15 × 8 = 1.20/km. Petrol at 15 km/L and 100/L: 100 ÷ 15 = 6.67/km. Over a year: 18,000 vs 100,000. Over five years: 90,000 vs 500,000 — a 410,000 energy gap. If this were the whole story, every driveway would already be electric.
The other half of the ledger
| Factor | Direction | Why it matters |
|---|---|---|
| Purchase premium | Against EV | In this example 400,000 — the payback on energy alone is 400,000 ÷ 82,000 ≈ 4.9 years |
| Charging access | Decisive | Home charging at domestic rates is the cheap case; public DC fast charging runs 2–3× per kWh, pushing EV cost/km toward 2.5–3.5 |
| Maintenance | For EV | No oil changes, less brake wear (regen), fewer moving parts — real but modest annual savings |
| Insurance | Often against EV | Higher repair costs can mean higher premiums; quote both before deciding |
| Depreciation | Uncertain | Battery-degradation fears pressure EV resale; petrol resale is better understood. This is the least quantifiable line |
Reading the payback honestly
The 4.9-year payback assumes the home-charging 1.20/km. Rerun it with fast-charge pricing (say 2.8/km average): annual saving drops to (6.67 − 2.8) × 15,000 ≈ 58,000, and payback stretches to about 6.9 years. Halve your annual distance to 7,500 km and the home-charging payback stretches to ~9.8 years — possibly longer than you keep the car. The three numbers that decide this purchase are annual km, charging access, and the premium you actually pay — everything else is rounding.
When each side wins
- EV wins clearly: high annual distance + home charging + state incentives shrinking the premium. The 410,000 five-year energy gap does the work.
- Petrol wins clearly: low annual distance + no home charging + a large purchase premium. The energy saving never repays the gap.
- Genuinely close: moderate distance with mixed charging — where maintenance savings vs insurance and depreciation decide it, and honest math should admit it's a toss-up.
FAQ
How much cheaper is an EV per km?
On home charging, roughly 5× cheaper: 1.20/km vs 6.67/km in the worked example. On public fast charging the gap narrows to roughly 2× — still significant, no longer decisive alone.
How long until an EV pays back its premium?
400,000 ÷ 82,000 ≈ 4.9 years with home charging at 15,000 km/year. Rerun the division with your own premium, distance and charging price — the answer swings from 3 to 10+ years.
Do EVs really need less maintenance?
Generally yes — no oil changes, fewer wear parts, regenerative braking extends brake life. Tyres and suspension wear similarly. Budget the savings, but don't let it carry the whole decision.
What's the biggest mistake in EV vs petrol comparisons?
Comparing energy only, or assuming home-charging rates for someone who will actually fast-charge. Both errors inflate EV savings; the honest model uses your real km, your real charging mix, and the real premium after incentives.
Run your own comparison
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