The honest answer depends on three things: how much you charge at home versus on the road, what tariff you're on, and how many miles you drive. We model all three and give you a straight comparison against the petrol equivalent.
EV electricity use = annual mileage ÷ efficiency. Real-world efficiency drops 15–25% in winter and on motorway runs above 70mph — pick a number that reflects your actual driving, not the WLTP figure on the spec sheet.
Charging mix matters more than people realise. At home on Octopus Go (8.5p), 8,000 miles costs ~£190. At public rapid chargers (65p), the same 8,000 miles costs ~£1,470 — nearly 8× more. The home/public split is the single biggest variable.
Petrol comparison uses UK gallons (4.546 litres). We don't include road tax, insurance, or maintenance — just fuel/charging. EVs typically save £200–£500/year on those too, but it's car-dependent.
CO₂: petrol emits ~2.31 kg per litre burned. Grid electricity ~0.207 kg/kWh (Defra 2025). Even on a coal-heavy grid an EV is cleaner per mile; on the UK's increasingly renewable grid the gap widens every year.
If you can't charge at home. Renting, on-street parking, or no driveway means relying on public chargers — and at 60–85p/kWh, a petrol car can be cheaper. Some local authority schemes are improving access; check yours.
Low-mileage drivers. Below ~5,000 miles a year, the petrol-vs-EV running cost gap shrinks below £400/year. The case to switch becomes more about emissions and convenience than savings.
If you're on a flat tariff. Without a TOU tariff like Octopus Go, home charging at 24.5p delivers a much weaker saving — typically half what Go customers achieve. Switching tariff before buying an EV often makes more difference than which EV you buy.
Estimates only. Actual EV efficiency varies enormously with driving style, climate, and tyre choice.