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CALCULATOR · Finance

EV vs Petrol Cost Calculator

Monthly costs of an electric car against a petrol one — savings, per-km rates and the break-even tariff.

Show formula
petrol = distance × consumption ÷ 100 × fuel price · ev = distance × consumption ÷ 100 ÷ charger efficiency × electricity price · savings = petrol − ev · year = month × 12

Inputs

How far the car drives in a typical month — the odometer between two fill-ups or charge sessions is the honest source.

Liters the petrol car burns per 100 km — the spec-sheet figure or your own trip-computer average.

The pump price for one liter (or one US gallon) — the figure on the forecourt sign.

kWh the EV uses per 100 km at the battery — the spec-sheet or EPA figure, or your trip-computer average.

Your price for one kWh at the meter — the home tariff if you charge overnight, the charger’s price if you don’t.

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Wall-to-battery losses. Home AC charging loses about 10% — the meter sees more than the battery gets.

Result

Your result appears here

Enter Distance per month and the result fills in as you type.

How it works

  1. Enter how far the car drives in a typical month — the odometer between two fill-ups is the most honest figure you have.
  2. Fill in the petrol side: its consumption and the pump price. Then the EV side: its kWh per 100 km or 100 miles, your price per kWh and, for home charging, the charger efficiency.
  3. Read the monthly and yearly savings, the two per-km rates, and the break-even electricity price — the tariff at which the two cars would cost the same.

Frequently asked questions

Which figure should I trust — the spec sheet or my own average?

Your own. The spec-sheet consumption is measured on a test cycle that flatters both kinds of car, and real driving is messier: cold mornings, short trips, roof boxes, highway speed. Put your trip-computer average in both sides and the comparison describes your driving, not the test bench — the break-even tariff moves with it.

What does the break-even electricity price tell me?

It is the tariff at which the two cars cost the same for the month you entered. Charge cheaper than that and the EV wins every month; pay more — a motorway fast charger on an expensive tariff, say — and the petrol car pulls ahead. It depends on the pump price and the two consumptions, not on how far you drive.

Does this include purchase price, insurance and maintenance?

No — this is the energy bill only, the piece that repeats every month. An EV usually spends less on servicing and more on depreciation, and those swings can dwarf a fuel saving in some years. Use this figure for the running-cost line in your budget, then add the ownership costs separately.

Examples

1,200 km a month: a petrol car at 7.0 L/100 km with fuel at 1.65/L, against an EV at 17 kWh/100 km on a 90%-efficient home charger at 0.30 per kWh
84 L and 138.60 at the pump against 226.67 kWh and 68.00 at the meter — 70.60 a month saved, 847.20 a year, and the EV stays ahead up to a tariff of 0.611 per kWh.
1,000 miles a month: 30 mpg at 3.40/gal against an EV at 28 kWh/100 mi on a 92%-efficient home charger at 0.15 per kWh
33.33 gal and 113.33 against 304.35 kWh and 45.65 — 67.68 a month saved, 812.17 a year, break-even at 0.372 per kWh.

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