Part of our guide to Car Payment Calculator
The EV running-cost argument is usually made with someone else's electricity price and someone else's mileage. Your own numbers give a different answer, sometimes the opposite one.
Annual fuel cost for each car at your prices and mileage, the difference per year, and — if the EV costs more up front — how long that premium takes to repay. Energy and purchase price only; everything else is named below rather than guessed at.
How the calculation works
petrol per year = (miles ÷ mpg) × price per gallon
electric per year = (miles ÷ 100) × kWh per 100 miles × price per kWh
break-even years = price difference ÷ annual savingThe break-even line only appears when the EV is both dearer to buy and cheaper to run. If it is cheaper on both, there is nothing to repay. If it is dearer on both, no length of ownership fixes that, and the calculator says so instead of returning a number.
What decides the answer
Where you charge. This is the single largest variable. Home overnight rates and public rapid-charging rates can differ by a factor of three or more. An EV charged at home is usually much cheaper to run than petrol; the same car charged exclusively on rapid chargers frequently is not.
How far you drive. Running-cost savings scale with mileage. A high-mileage driver repays a purchase premium quickly. Someone driving 5,000 miles a year may never repay it at all.
What you are comparing against. A thirsty petrol car makes the EV look excellent. An efficient hybrid narrows the gap considerably.
What this deliberately leaves out
Insurance, servicing, tyres and depreciation all differ between the two, and all vary far too much by specific vehicle to state honestly here. Putting plausible-looking figures on them would be guessing dressed up as arithmetic — and those numbers would then drive real purchase decisions.
Get an insurance quote on both specific cars. That single figure moves the comparison more than most of the inputs above.
Tax credits and grants change frequently and by jurisdiction. If you qualify for one, subtract it from the price difference before entering it.
Related tools and reading
This is an estimate for general information, not financial or purchasing advice — see our disclaimer.
Frequently asked questions
What does kWh per 100 miles mean?
How much electricity the car uses to travel 100 miles — the EV equivalent of fuel consumption. Lower is more efficient. It is on the window sticker and in the specifications.
Why does home charging change the answer so much?
Public rapid charging can cost several times the home rate. An EV charged at home is usually much cheaper to run than petrol; the same car charged exclusively on rapid chargers often is not.
Does this include servicing and insurance?
No, deliberately. Both differ between the two and vary too much by vehicle to state honestly. This compares energy and purchase price only, and says so.
What about tax credits or grants?
Subtract any you actually qualify for from the price difference before entering it. They change frequently and by jurisdiction, so this does not guess at them.
What if there is no break-even?
If the EV costs more to buy and more to run at your prices, there is no payback point and the calculator says so rather than inventing one.
Sources
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