How to use this calculator
- Enter or choose distance driven per year.
- Enter or choose eV energy use.
- Enter or choose charging efficiency.
- Enter or choose electricity price per kWh.
- Enter or choose petrol car fuel use.
- The eV saving per year updates as you type. Use Copy result or Share to keep it.
Method
EV kWh = km × kWh/100 km ÷ 100 ÷ Charging efficiency; EV cost = EV kWh × Price + Maintenance; Petrol cost = km × L/100 km ÷ 100 × Price + Maintenance; Saving = Petrol cost − EV cost
- km
- distance per year
- Charging efficiency
- share of purchased electricity stored in the battery
Worked example
- EV: 15,000 × 17 ÷ 100 = 2,550 kWh ÷ 0.90 = 2,833.33 kWh × 0.25 = 708.33.
- Petrol: 15,000 × 7 ÷ 100 = 1,050 L × 1.80 = 1,890.
- Saving = 1,890 − 708.33 = 1,181.67 a year.
Over 15,000 km a year the EV costs 708.33 in electricity against 1,890 in petrol, saving 1,181.67.
What the result means
The gap depends mostly on the electricity price you pay; public rapid charging can cost several times more than off-peak home charging. Use the yearly saving with the price difference between the cars to estimate a payback period.
Assumptions and limits
- Distances in kilometres and fuel use in L/100 km.
- Prices stay constant for the year.
- Purchase price, depreciation, insurance, road tax and financing are not included.
Questions
My petrol car is rated in MPG. How do I convert?
L/100 km = 282.481 ÷ UK MPG, or 235.215 ÷ US MPG.
Are EV maintenance costs really lower?
EVs have no oil changes and less brake wear, but tyres may wear faster. Enter quotes or your own records rather than assuming a figure.