Advanced options
Fuel only: insurance, servicing (typically lower for EVs), depreciation and any public charging subscriptions sit outside this sum. The charging rate dominates the whole comparison: home overnight tariffs make EVs a fraction of petrol's cost, motorway rapids can exceed it.
What The EV vs Petrol Calculator Works Out
- Petrol cost per mile: the price per litre multiplied by 4.546 litres to the UK gallon, divided by mpg. Petrol at GBP 1.45 a litre in a 40mpg car costs about 16.5p a mile; a 30mpg SUV is nearer 22p.
- EV cost per mile: the electricity price divided by the car's efficiency. At 3.5 miles per kWh that is about 7.5p at the standard home rate (the current Ofgem price cap unit rate), 2p on a 7p overnight EV tariff, and over 20p at motorway rapid prices. The same car costs ten times more per mile at a motorway rapid than on a driveway overnight, which is the entire story.
- Annual difference: the gap per mile multiplied by your annual mileage. An 8,000-mile year saves around GBP 700 at standard home rates, well over GBP 1,000 on an overnight tariff, and roughly breaks even for a driver dependent on public rapids.
- Share of miles charged at public rapids (advanced): few drivers charge in one place. Enter the proportion done at public rapids and their price and the EV figure uses a blended rate. Home electricity carries 5% VAT and public charging 20%, the gap behind the fairness debate.
- Charging losses (advanced): roughly 10% of the electricity drawn becomes heat rather than range, more on a 3-pin plug. The simple comparison ignores this; add it here for an honest figure.
- Extra fixed costs and servicing saving (advanced): EVs often cost a little more to insure and, on newer cars, to depreciate, and they now pay road tax including the expensive-car supplement where applicable; against that they have no oil changes and minimal brake wear, typically saving GBP 100 to GBP 200 a year on servicing. The "including fixed costs" card nets these off.
- Over N years (advanced): the all-in annual difference multiplied by the years you will keep the car, at today's prices.
- Break-even charging price (advanced): the electricity price per kWh at which the EV costs exactly the same per mile as the petrol car. If your realistic average is below it, the EV wins on fuel; smart tariffs and scheduled charging make the cheap case nearly automatic for anyone with off-street parking.
- CO2 saved per year (advanced): petrol at 2.31kg of CO2 per litre against the EV's electricity at about 0.207kg per kWh of UK grid power, which keeps falling as more wind and solar come on. Company car drivers live in a different equation again, where low benefit-in-kind rates make an EV overwhelmingly the tax-efficient choice.