EV Charging Cost Calculator
The battery takes 45 kWh. The meter sees more.
EV Charging Cost Calculator
Compare a home charge with a public charger after charging losses, and see the cost per mile or kilometre.
Energy lost as heat
Prices are yours to enter: electricity tariffs and public charging networks vary by region and by time of day. The 10% loss default is a planning assumption, not a measurement of your car.
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What This Calculator Does
The EV Charging Cost Calculator prices a charging session from the battery size and the charge window, then compares a home tariff with a public charger. It separates the energy that reaches the battery from the energy drawn from the grid, so charging losses are visible rather than quietly missing from the bill.
How It Works
Usable battery capacity is multiplied by the change in charge percentage to get the energy added to the battery. Charging is not perfectly efficient, so the grid energy is that figure divided by (1 - loss percentage). Grid energy is multiplied by the home and public price per kWh. Range added is the battery energy multiplied by the car efficiency in miles or kilometres per kWh, and charging time is grid energy divided by charger power.
Example
A 75 kWh car charged from 20% to 80% takes on 45 kWh. With 10% charging loss the meter supplies 45 / 0.90 = 50 kWh. At $0.16 per kWh that is $8.00 at home; at $0.45 per kWh it is $22.50 at a public charger. At 3.5 miles per kWh the session adds 157.5 miles, which is about $0.051 per mile at home.
Formula
battery kWh x (end % - start %) / 100energy added / (1 - loss % / 100)grid energy x price per kWhenergy added x distance per kWhgrid energy / charger kWHours; multiplied by 60 for minutes.
Reading the Results
Grid energy drawn
The electricity the meter actually supplies. It is higher than the energy stored in the battery because chargers and batteries lose some energy as heat.
Home cost
Grid energy multiplied by your home tariff. Time-of-use rates, standing charges, and solar export credits are not modelled; use the effective rate you pay for the charging window.
Cost per mile
The session cost divided by the range it adds. This is the number to compare with petrol or diesel cost per mile, and it moves with both electricity price and driving efficiency.
Sources and References
U.S. Department of Energy - Fuel Economy: Electric Vehicles
How EV efficiency is measured and reported
Explains miles per kWh and kWh per 100 miles. Real efficiency varies with speed, temperature, and driving style.
U.S. Environmental Protection Agency - Fuel Economy
Monroney label efficiency figures for new vehicles
The source of the efficiency number on a new car label. Use your own trip meter for a used car in your conditions.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
Why is grid energy higher than the energy added to the battery?
Charging loses energy in the onboard charger, the cable, and the battery itself, mostly as heat. The default 10% is a planning assumption. Cold weather, high charging power, and battery age can push losses higher.
Why is public charging so much more expensive?
Public networks pay for equipment, land, demand charges, maintenance, and payment processing, and they price for convenience. The gap in the calculator is the premium you pay for charging away from home, not a statement about the cost of electricity.
Should I use the car efficiency from the label or the trip meter?
Use the trip meter for a car you already drive, especially in winter or at highway speed. The label figure is a standardised test result and is useful for comparing models, not for predicting a specific journey.
Does this include battery degradation or replacement?
No. It prices energy for one session. Depreciation, tyres, servicing, insurance, and any battery repair belong in a total cost of ownership calculation, not in a charging cost.
How do I convert kWh per 100 miles into miles per kWh?
Divide 100 by the kWh per 100 miles figure. For example, 28 kWh per 100 miles is 100 / 28 = 3.57 miles per kWh. For kilometres, the same relationship holds with km per kWh.