Loading EV vs Petrol Running Cost…
Fuel against electricity over a year of your own driving, at the prices you actually pay. This is the running-cost line only, and on a car purchase it is rarely the biggest one.
Both sides must be typed in the same one. Nothing is converted here.
Energy billed at the meter that never reaches the battery. Set it from your own reading.
The rate you charge on, which may not be your daytime rate.
Name the gallon: the two differ by a fifth.
Electric is cheaper by 89.71 USD a year
823.53 USD of electricity against 913.24 USD of fuel
Purchase price, depreciation, insurance, tax, servicing, tyres and the cost of installing a charger are all outside this comparison, and together they usually dwarf it. A car that wins on pence per mile can still be the more expensive car to own.
The two tie-point prices are the useful output when prices move. They say what the fuel would have to cost, or what electricity would have to cost, before the answer flips — which is a more durable thing to know than today’s winner.
Electric against petrol is usually argued with half-remembered figures, and the half that gets remembered is whichever one suited the person quoting it. The comparison only means something when both sides are built from prices you personally pay and driving you personally do, which is all this page asks for: a year of distance, what each car uses, and the two prices.
It compares energy and fuel and stops there. Purchase price, the discount you negotiated, depreciation over three years, insurance, road tax, servicing, tyres and the cost of getting a charger fitted are all outside it, and on a new car those items are usually much larger than the running-cost line. Treat the answer as one input to a decision rather than the decision.
The electric side works in energy off the meter. Consumption goes in as miles per kWh or kWh per 100 km, whichever your car displays, and the charging loss is added on top so the electricity being priced is the electricity you are billed for rather than the portion that reached the battery.
The petrol side works in volume, and volume depends on which gallon the economy figure was quoted in. A car described as 40 mpg in Britain buys 4.546 litres per gallon; the same phrase in the United States buys 3.785. Choosing the wrong one moves the fuel bill by a fifth, which is more than enough to flip the verdict, so the unit is picked explicitly and the price is entered per the same unit.
Say 10,000 miles a year, an electric car managing 4 miles per kWh with a fifth of the metered energy lost to charging, electricity at 0.20 a unit, against a petrol car returning 25 mpg on US gallons at 4.00 a gallon.
The electric car needs 2,500 kWh in the battery, so 3,125 off the meter, costing 625 — 6.25 a hundred miles. The petrol car burns 400 gallons at 1,600, or 16 a hundred miles. The gap is 975 a year, and it comes as much from the price per unit of energy as from the efficiency of the two drivetrains.
Today’s winner is a fact about today’s prices, and prices move. More useful are the two break-even figures printed above: the fuel price at which the petrol car would cost exactly what the electric one costs, and the electricity price at which the reverse is true. In the example, petrol would have to fall to 1.56 a gallon, or electricity climb to 0.51 a unit, before the ranking changed.
Those two numbers are what to carry around, because they tell you how much headroom the answer has. A verdict that survives a doubling of the electricity price is a robust verdict; one that flips on a five per cent move is not really a verdict at all. They are also the honest way to handle public charging, which can be several times a domestic rate: run the comparison twice, once on your home tariff and once on the rate you would pay on a long trip, and see whether the conclusion holds at both.
Work out a weighted rate, or run the tool twice for the two extremes. Somebody charging overnight at home most weeks and rapid-charging on occasional long trips has a blended cost, and using either figure alone gives an answer that is wrong in a predictable direction.
It is one line of the accounts, not a recommendation. Running costs can favour electricity while the total cost of ownership favours keeping a paid-off petrol car for another three years, because nothing you already own has to be bought again.
Because the imperial gallon is 20% larger than the US one, an economy figure without its unit is ambiguous by that much. Pick the unit your figure was quoted in, and enter the price for the same unit, or the comparison compares two different cars.
Run both sides for the share of miles each covers: electric miles at your charging cost, engine miles at your fuel cost, then add them. A plug-in driven by somebody who rarely plugs it in is simply a heavy petrol car, and its official figures will not say so.