EV Charging Cost Calculator - Cost per Mile, km & Month

Formula

wall energy (kWh) = energy added (kWh) / efficiency

cost = wall energy (kWh) x electricity price per kWh + session fee

Example

Adding 45 kWh at 90% efficiency uses about 50 kWh from the wall. At 0.28 per kWh plus a 1.50 session fee, the estimated total is 15.50.

How the entered electricity price changes one session

Each row uses 45 kWh added to the battery and 90% charging efficiency, which means about 50 kWh purchased from the wall.

These are illustrative inputs, not current market prices. Use one currency consistently and enter the current all-in rate from your bill, app, or station.

Assumptions and limits

• The calculator does not use live charging prices.
• Public charging prices may include time-based, idle, congestion, tax, or membership fees.
• Use the rate shown on your utility bill, charging app, or station screen.
• This is not a bill, tax, or receipt estimate unless you manually include the relevant fees and taxes.

How to read the result

Wall energy is the estimated electricity purchased for the session. Energy cost multiplies wall energy by the rate you enter, and total cost adds any fixed session fee you include.

• Wall energy is higher than battery energy when efficiency is below 100%.
• Energy cost uses only the per-kWh price entered in the form.
• Total cost includes the optional session fee but not taxes or fees you leave out.
• Cost per mile, cost per km, and cost per 100 distance units use the vehicle efficiency you enter.
• Monthly and annual estimates can use repeated sessions, monthly miles, monthly kilometers, or a combination depending on which fields you fill.
• Driving monthly cost converts monthly miles into battery kWh, adjusts for charging efficiency, and applies the price per kWh.
• Metric monthly cost does the same calculation from monthly kilometers and km/kWh.
• The number can differ from a real receipt if the station adds idle fees, time fees, taxes, or discounts.

Worked examples

Cost estimates are easiest to verify when you compare home bill values, public charging app prices, and receipt-style session fees separately.

• Home charging: 45 kWh added at 90% efficiency uses about 50 kWh from the wall. At 0.16 per kWh, the energy estimate is 8.00.
• Public AC charging: 35.2 kWh at 0.30 per kWh plus a 1.00 session fee estimates to 11.56 before taxes.
• DC fast charging: 45 kWh at 0.48 per kWh plus a 2.00 session fee estimates to 26.00 before idle or membership adjustments.
• Cost per mile example: 45 kWh at 3.5 miles/kWh covers about 157.5 miles, so a 15.50 session is about 0.10 per mile.
• Cost per km example: 45 kWh at 5.6 km/kWh covers about 252 km, so a 15.50 session is about 0.06 per km.
• Cost per 100 km example: the same session is about 6.15 per 100 km before taxes, idle fees, or public charging discounts.
• Session-based monthly example: if the same 15.50 session happens four times per month, the planning estimate is about 62.00 per month and 744.00 per year.
• Driving-based monthly example: 1,000 miles at 3.5 miles/kWh needs about 286 battery kWh. At 90% efficiency and 0.16 per kWh, wall energy is about 317 kWh and energy cost is about 50.79.
• Metric monthly example: 1,600 km at 5.6 km/kWh also needs about 286 battery kWh before charging losses, about 317 wall kWh at 90% efficiency, and about 50.79 at 0.16 per kWh.
• Low efficiency example: if charging efficiency drops from 90% to 82%, the same 45 kWh battery-side session uses about 54.9 kWh from the wall.

Common input mistakes

A cost estimate can look precise while still missing important billing details. Check whether your rate is energy-only, all-in, time-of-use, or a public charging app price.

• Entering battery kWh added but forgetting efficiency loss.
• Using a public price without session fees, idle fees, taxes, or membership discounts.
• Using a national average instead of the rate on your own utility bill.
• Mixing an energy-only home rate with an all-in public charging receipt.
• Forgetting that time-of-use plans can have different rates by hour.
• Using a lifetime efficiency number when current highway, winter, or city efficiency is very different.
• Entering charges per month when you really want a monthly driving-mile budget, or entering both without understanding that they answer different questions.
• Mixing mi/kWh and km/kWh values without changing the matching monthly distance field.
• Treating monthly or annual totals as a bill forecast when taxes, fixed fees, and behavior can change.

What to check next

For a real budgeting estimate, verify the rate from the original source rather than copying an example number.

• Utility bill or tariff page for home electricity price.
• Charging app or station screen for current public price and fixed fees.
• Charging receipt for delivered kWh, fees, taxes, and discounts.
• Recent miles/kWh from the dashboard when estimating cost per mile.
• Monthly miles from your odometer, app, commute estimate, or recent driving history when estimating a household monthly budget.
• Monthly kilometers and km/kWh when you plan in metric units.
• Home vs public calculator when comparing the same session across two charging options.

FAQ