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EV Charging Cost Calculator

Estimate what it costs to charge an electric car from its battery size, how much charge you add, your electricity price and an assumed charging efficiency.

kilowatt-hours

The usable capacity, which can be less than the headline battery size.

percent

Battery level before charging.

percent

Battery level you will charge to.

per kilowatt-hour

In any currency. The cost uses the same currency.

percent

An assumption. Charging losses vary by vehicle, charger, temperature and conditions. Adjust this value if you know your charging efficiency.

Results

Estimated charging cost

15.00

In the same currency as your electricity price.

Battery energy added
45 kWh
Electricity used
50 kWh
Charging loss
5 kWh
Charge added
60 %

Estimated charging cost 15.00. 50 kilowatt-hours of electricity for 45 kilowatt-hours added to the battery.

Formula

Charge added (%)
= target charge − starting charge
Battery energy added (kWh)
= usable battery capacity (kWh) × charge added ÷ 100
Electricity used (kWh)
= battery energy added ÷ (charging efficiency ÷ 100)
Charging loss (kWh)
= electricity used − battery energy added
Charging cost
= electricity used (kWh) × price per kWh

Some electricity is lost as heat in the charger, cable and battery, so more is drawn than ends up stored. Dividing by the efficiency accounts for this.

Worked example

An EV with a 75 kWh usable battery charges from 20% to 80%. Electricity costs 0.30 per kWh, and charging is assumed to be 90% efficient.

  1. Step 1: Charge added

    80 − 20 = 60%

  2. Step 2: Battery energy added

    75 × 60 ÷ 100 = 45 kWh

  3. Step 3: Electricity used

    45 ÷ 0.9 = 50 kWh

  4. Step 4: Charging loss

    50 − 45 = 5 kWh

  5. Step 5: Charging cost

    50 × 0.30 = 15.00

Adding 45 kWh to the battery draws about 50 kWh of electricity and costs about 15.00, in whichever currency the price was given.

Choosing a charging efficiency

Charging efficiency is an assumption, not a fixed property of your car. Losses vary with the vehicle, the charger, the charging power, the temperature and whether the battery needs heating or cooling while it charges. The default is only a starting point.

To measure your own figure, note how many kWh your charger app or home meter recorded for a charge and how much charge the car gained. Divide the battery energy added by the kWh recorded and multiply by 100.

What the price should include

The calculator multiplies electricity used by a single price per kWh. Real costs can be more complicated:

  • Home tariffs vary widely, and time-of-use tariffs charge different rates at different times of day.
  • Public chargers may add session fees, per-minute charges or idle fees on top of, or instead of, a price per kWh.
  • If your charger or app reports the kWh a session used, you can multiply that figure by your price directly.

Usable versus advertised battery capacity

Manufacturers sometimes quote a gross battery capacity that is larger than the usable capacity the car can actually charge and discharge. Capacity can also decline as a battery ages. Use the usable figure if you can find it, as the result scales directly with it.

Frequently asked questions

How do I calculate the cost to charge an electric car?

Multiply the usable battery capacity by the percentage of charge you add to get the energy stored, divide by the charging efficiency to include losses, then multiply by the price per kWh. For a 75 kWh battery charged from 20% to 80% at 0.30 per kWh and 90% efficiency, that is 15.00.

How much does a full charge cost?

Set the starting charge to 0% and the target to 100%. With the same 75 kWh battery, price and efficiency, a full charge from empty uses about 83.33 kWh and costs about 25.00. In practice most charges start with some energy left in the battery.

What charging efficiency should I use?

Use your own measured figure if you have one. Otherwise, treat the default as an assumption and try a few values to see how much the cost changes. The calculator cannot know the actual losses for your car and charger.

Why is the electricity used higher than the energy added to the battery?

Some energy is lost as heat while charging, in the charger, the cable and the battery, and some may be used to heat or cool the battery. You pay for the electricity drawn, including those losses.

Which currency does the calculator use?

Any currency. Enter the electricity price per kWh in your local currency and the cost is shown in that same currency. The calculator does not convert currencies or look up tariffs.

Does it include public charging fees?

No. It uses a single price per kWh. Session, per-minute and idle fees are not included, so add them separately if your charger uses them.

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