Petrol vs Electric Car Running Cost Calculator

Petrol vs electric: what really drives the cost

The headline that an electric car is “cheaper to run” is true far more often than not in the UK — but how much cheaper depends almost entirely on one thing: where you charge. Charging at home on a standard or off-peak tariff is dramatically cheaper than petrol per mile. Relying on public rapid chargers can narrow the gap to almost nothing, and occasionally reverse it. This calculator lets you model your own split rather than trust an averaged claim.

The home-charging advantage

A typical efficient EV travels around 3.5–4 miles per kWh. At a home electricity rate of roughly 25p/kWh that works out near 6–7p per mile. A dedicated overnight EV tariff (often around 7–9p/kWh for a few hours) can push that below 3p per mile. By contrast, a 45mpg petrol car at 140p per litre costs in the region of 14p per mile. That is the core of the saving: on home charging, an EV’s “fuel” is roughly a third to a fifth of petrol’s cost.

Why public charging changes the maths

Public rapid and ultra-rapid chargers are priced for convenience, commonly 55–80p/kWh. At those rates an EV can cost 15–22p per mile — similar to, or more than, a petrol car. If you cannot charge at home and would depend on public chargers for most miles, the running-cost case for an EV weakens sharply, and the decision rests more on emissions, refinement and company-car tax than on fuel savings. Set the “% charged at home” slider honestly: it is the single biggest lever in the result above.

Costs this calculator does not include

Running cost is only part of total cost of ownership. An EV usually has a higher purchase price, though that gap is closing and is offset on lease or PCP by lower monthly fuel spend. EVs typically have lower servicing and maintenance costs (no oil changes, less brake wear thanks to regenerative braking) but tyres can wear faster due to weight and torque. From April 2025, electric cars in the UK no longer escape Vehicle Excise Duty (road tax). Insurance can be higher on some EV models. Depreciation varies widely by model. Treat the annual saving above as the fuel-versus-electricity picture, and weigh it against these other lines before deciding.

When an EV clearly wins

• You can charge at home, ideally on an off-peak overnight tariff.
• You drive a meaningful annual mileage, so the per-mile saving compounds.
• You are a company-car driver benefiting from low Benefit-in-Kind tax on EVs.

Conversely, low-mileage drivers with no home charger and no off-street parking will see a much smaller running-cost saving, and should look hard at the upfront and public-charging numbers before switching.

FAQ

Is it always cheaper to run an electric car?

No. On home or off-peak charging it is usually far cheaper per mile than petrol. If you rely on public rapid chargers for most of your miles, the cost can match or exceed a petrol car. Your charging mix decides it.

What is a realistic EV efficiency figure?

Many mainstream EVs achieve about 3.5–4.2 miles per kWh in mixed driving; larger or performance models and cold winter motorway runs can drop to 2.5–3. Use your car’s real trip-computer figure for the most accurate result.

Does this include the cost of a home charger?

No. A home wallbox is a one-off cost (commonly several hundred pounds installed). It pays back over time through cheaper charging, but it is separate from the annual running cost shown here.