Electric Car vs Petrol Calculator

What this comparison actually measures

An electric car usually costs more to buy and less to run, so the whole question is how many years of cheaper running it takes to recover the higher price. This calculator answers exactly that and nothing more: it compares fuel against electricity, divides the price premium by the annual saving, and reports the break-even in years. Maintenance, tax, insurance, depreciation and charger installation are all outside it.

Two assumptions are fixed inside the model rather than entered: petrol consumption of 30 miles per gallon, measured against the imperial gallon of 4.546 litres, and electric consumption of 4 miles per kWh. Neither is an input, so a more efficient petrol car or a less efficient EV cannot be modelled directly. The electricity price is entered in hundredths of your currency per kWh, so a rate of 0.10 is entered as 10.

Where the running-cost gap comes from

On the built-in efficiencies, petrol at 1.50 a litre works out at 0.2273 a mile, since 30 miles per imperial gallon is 0.1515 litres a mile. Electricity at 0.10 per kWh works out at 0.025 a mile, because 4 miles per kWh is 0.25 kWh a mile. That is roughly a ninefold difference in fuel cost per mile at those prices, and it is the entire engine of the comparison. Electric drivetrains also have fewer wearing parts, no oil changes and no clutch, and regenerative braking reduces friction-brake wear, but none of that maintenance difference is in the calculation.

Where petrol still wins

The purchase premium is the obvious one, and this tool takes it directly from the two prices you enter rather than assuming a figure. Depreciation is the quieter one: residual values for electric models have been less predictable than for established petrol models, and none of that is modelled here, so a comparison built only on fuel understates the risk on the resale side. Charging access is the decisive practical factor. Public rapid charging can cost several times a home overnight rate, and at a rate of 0.60 per kWh, entered as 60, the same 10,000-mile year takes the break-even from 4.9 years to 12.9. Where charging at home is not possible, entering the public rate is the honest version of the calculation.

The break-even maths

The premium divided by the annual fuel saving. Worked through on the example figures: a 35,000 EV against a 25,000 petrol car is a 10,000 premium. At 10,000 miles a year, petrol costs 10,000 divided by 30, times 4.546 litres, times 1.50, or 2,273.05. Electricity costs 10,000 divided by 4, times 0.10, or 250.00. The saving is 2,023.05 a year, so the break-even is 10,000 divided by 2,023.05, which is 4.9 years, with 10,115.23 saved across five.

Mileage moves it almost proportionally. At 20,000 miles a year the same premium clears in 2.5 years. At 6,000 miles a year it takes 8.2 years, which is long enough that the car may well be sold before the arithmetic completes.

Charging access dominates the result

The single largest variable is not the car, it is where it charges. A home overnight rate and a motorway rapid charger can differ severalfold per kWh, and since electricity is the whole of the EV running cost in this model, that difference passes straight through to the break-even. The practical questions are whether off-street parking allows a charger at all, what overnight rate is available, and whether the driving pattern is mostly local or mostly long-distance. A driver who charges at home and drives regionally is the case where this arithmetic works; a driver dependent on public rapid charging is the case where it may not.

Non-financial factors

Electric cars are quieter, deliver torque immediately, need fewer service visits and produce no tailpipe emissions. On full life-cycle emissions rather than tailpipe alone, the ICCT's global comparison of combustion and electric passenger cars assesses Europe, the United States, China and India separately, covering markets that account for around 70% of global car sales, because the answer depends on how the local grid generates its electricity. Petrol keeps a denser refuelling network, faster refuelling and, in most markets, a wider used-car choice. Some cities charge access fees that vary by emissions, which sits outside this calculation entirely.

What the calculator does not include

Maintenance and servicing, vehicle taxes, insurance, charger installation, depreciation and resale value, battery replacement, purchase incentives and any local subsidy. It also holds both energy prices flat for the whole period, which over a break-even measured in years is a strong assumption in both directions. For the market context behind those moving parts, the IEA's Global EV Outlook tracks sales, battery costs and charging infrastructure across regions each year. The output here is one line of a total-cost picture: pair it with insurance quotes and a depreciation estimate for the specific models being compared.