Calculating Your EV's True Cost Per Mile, With a Worked Example
Multiplying an EV's energy consumption rate (kilowatt-hours per 100 miles, commonly listed in vehicle specifications) by the local electricity rate per kilowatt-hour, then dividing by 100, gives a true cost-per-mile figure directly comparable to a gas vehicle's cost-per-mile (fuel price divided by miles per gallon).
This calculation puts EV and gas vehicle running costs on the same comparable footing, which a simple "electricity is cheaper than gas" intuition doesn't precisely quantify.
A worked example
An EV rated at 30 kWh per 100 miles, charged at a home electricity rate of $0.15/kWh: 30 × $0.15 = $4.50 to travel 100 miles, or $0.045 per mile. Comparing this to a gas vehicle averaging 30 mpg at $3.50/gallon: $3.50 ÷ 30 = about $0.117 per mile — in this example, the EV's per-mile cost is meaningfully lower.
Why home charging rate matters so much to this comparison
The electricity rate used has a significant direct effect on the calculated cost-per-mile — a lower home electricity rate makes an EV's cost advantage larger, while a higher rate (or reliance on more expensive public fast charging) narrows or can even eliminate that advantage, which is why using an accurate, specific electricity rate matters for a meaningful comparison.
Where to find an EV's energy consumption rating
Most EVs have an official energy consumption rating (kWh per 100 miles, or an equivalent efficiency figure) published by the manufacturer or a standardized testing agency — using this official figure, rather than a rough guess, gives a more accurate basis for the cost-per-mile calculation.