EV Charging Cost Per Mile Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

kWh: A kilowatt-hour is a unit of electricity. In this calculator, it is the amount of electricity your EV uses for driving and charging.

Efficiency format: The way your EV efficiency number is written, such as miles per kWh, kWh per 100 miles, or MPGe.

Miles per kWh: How many miles the EV can drive on 1 kWh of electricity. Higher is better.

kWh per 100 miles: How much electricity the EV uses to drive 100 miles. Lower is better.

MPGe: Miles per gallon equivalent, a label format used for electric vehicles on US fuel economy labels [4].

Blended electricity price: The average $ per kWh after mixing home charging and public charging by the percent of miles charged away from home.

Extra charging loss: Extra electricity used between the outlet and the battery. Leave it at 0 when your efficiency already includes wall electricity.

Break-even gas price: The gas price where the gas car and EV have the same energy cost per mile.

Mistake: Choosing the wrong Efficiency format for EV efficiency.
Fix: Match Efficiency format to the number you have before entering EV efficiency.

Mistake: Entering a bill total instead of Electricity price.
Fix: Use the per-kWh rate for Electricity price, including delivery charges if you want a real bill estimate.

Mistake: Putting yearly miles into Miles driven per month.
Fix: Divide yearly miles by 12 before entering Miles driven per month.

Mistake: Setting Miles charged away from home to 100 when only road trips use public charging.
Fix: Estimate the percent of total miles that use paid public charging, then enter that in Miles charged away from home.

Mistake: Adding Extra charging loss when EV efficiency already came from an EPA-style label or wall-based charging report.
Fix: Leave Extra charging loss at 0 unless your EV efficiency is based on battery or dashboard energy only.

Mistake: Treating negative EV savings versus gas as an error.
Fix: Negative EV savings versus gas means the entered EV charging mix costs more per mile than the gas comparison.

• The result is an energy-cost estimate only. It does not include charger idle fees, parking fees, membership fees, battery wear, maintenance, insurance, taxes, or vehicle purchase price.
• Electricity price should be your all-in $ per kWh. If you use only the energy charge and leave out delivery or demand charges, monthly cost can be too low.
• Extra charging loss is optional because some efficiency values already include wall energy. Adding loss to an EPA-style or wall-based value can double-count losses.
• Public charging is averaged by miles, not by exact charger sessions. A few expensive fast-charging stops can be hidden if the percent is guessed too low.
• Gas comparison outputs depend on Gas car efficiency and Gas price. They do not compare oil changes, repairs, depreciation, or taxes.
• Driving speed, weather, tires, cabin heat, air conditioning, hills, cargo, and battery temperature can change real EV efficiency.
• Monthly and yearly costs assume the entered Miles driven per month stays the same all year.

Calculation flow

The calculator first converts the entered EV efficiency into miles per kWh so every format can use the same math. EPA electric vehicle labels can show MPGe, so the MPGe option is converted before costs are calculated [4].

If Efficiency format = Miles per kWh: miles_per_kwh = EV efficiency

If Efficiency format = kWh per 100 miles: miles_per_kwh = 100 / EV efficiency

If Efficiency format = MPGe: miles_per_kwh = EV efficiency / 33.705

Next, the calculator finds electricity used per mile from the outlet. Extra charging loss increases outlet electricity only when you enter a loss percent.

wall_kwh_per_mile = (1 / miles_per_kwh) / (1 - Extra charging loss / 100)

Then it blends home and public charging prices using Miles charged away from home.

blended_price_per_kwh = Electricity price * (1 - Miles charged away from home / 100) + Public charging price * (Miles charged away from home / 100)

The main EV cost is electricity per mile times the blended electricity price. Per-mile energy cost is a common way to compare electric and gas driving costs [3].

ev_cost_per_mile = wall_kwh_per_mile * blended_price_per_kwh

EV cost per mile = ev_cost_per_mile * 100 cents

EV cost per 100 miles = ev_cost_per_mile * 100

Estimated monthly charging cost = ev_cost_per_mile * Miles driven per month

Estimated yearly charging cost = Estimated monthly charging cost * 12

Gas comparison

The gas comparison converts gas cost into $ per mile, then subtracts EV cost per mile. Savings are signed, so a negative value means the EV costs more for the entered prices.

gas_cost_per_mile = Gas price / Gas car efficiency

EV savings versus gas = gas_cost_per_mile - ev_cost_per_mile

Monthly savings versus gas = EV savings versus gas * Miles driven per month

Gas price that would tie the EV = ev_cost_per_mile * Gas car efficiency

Worked example

Suppose an EV gets 3.5 miles per kWh, electricity costs $0.17 per kWh, monthly driving is 1,000 miles, Extra charging loss is 10 percent, and all charging is at home. The outlet electricity is (1 / 3.5) / (1 - 0.10) = 0.31746 kWh per mile. The EV cost is 0.31746 * $0.17 = $0.05397 per mile, or 5.40 cents per mile. For 1,000 miles per month, estimated monthly charging cost is $53.97 and estimated yearly charging cost is $647.62. If the comparison gas car gets 30 mpg and gas costs $3.50 per gallon, gas costs $0.11667 per mile, so the EV saves about $0.06270 per mile, or $62.70 per month.