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EV Charging Cost Calculator with Charging Losses

Calculate the billed energy and cost needed to move from your starting charge to a target charge. Efficiency and tariff are supplied assumptions; idle, parking and time-based fees are not inferred.

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Your numbers

kWh
%
%
%
€/kWh
€
Your figures stay on this device.

How the calculation works

Charging losses mean the electricity billed can exceed the energy stored in an EV battery. This calculator starts with the desired increase in usable battery charge, then accounts for efficiency and a supplied electricity tariff.

Stored energy = usable capacity × charge increase. Billed energy = stored energy ÷ efficiency. Cost = billed energy × tariff + session fee.

  1. Find stored energy required

    Multiply usable capacity by the difference between target and starting charge, expressed as a fraction. This is energy added to the battery, not yet the amount bought.

  2. Allow for charging losses

    Divide stored energy by efficiency as a decimal. The operation is division because the purchased energy must cover both useful storage and losses.

  3. Calculate the session cost

    Multiply billed kWh by the electricity price and add the entered fixed session fee. No time-based fee is inferred from charging power or duration.

Worked example: Losses

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example adds 60% of a usable 50 kWh battery, or 30 kWh. At 90% efficiency it requires 33.3333 billed kWh; multiplying by 0.30 gives a charging cost of 10 with no session fee.

Usable battery capacity (kWh)
50
Starting charge (%)
20
Target charge (%)
80
Charging efficiency (%)
90
Electricity price (€/kWh)
0.3
Session fee (€)
0

Expected result

Charging cost
€10.00
Worked example: Full efficient session

Sample inputs demonstrate the method. They are not a forecast or product offer.

Usable battery capacity (kWh)
40
Starting charge (%)
0
Target charge (%)
100
Charging efficiency (%)
100
Electricity price (€/kWh)
0.2
Session fee (€)
2

Expected result

Charging cost
€10.00

Understanding your result

The output separates energy from cost so a change in tariff does not appear to change charging efficiency. Repeated sessions can differ if starting charge or losses change.

The efficiency is an assumption, not a measurement of a specific charger. Temperature, charging conditions and vehicle behaviour are not inferred from battery size.

Questions you might have

What does this ev charging cost calculator include?

Estimate a charging session from usable battery capacity, starting and target charge, charging efficiency and your tariff.

Which assumptions should I check?

Efficiency is a scenario assumption, not a guarantee for your charger. Time-based, idle and parking fees are not inferred.

Choosing the right inputs

Usable battery capacity
Use usable battery capacity in kWh rather than automatically copying the larger gross capacity advertised for a vehicle.
Starting charge
Enter the starting state of charge as a percentage and choose a target at or above it. The difference determines the share of battery capacity to replenish.
Charging efficiency
Enter a percentage efficiency for the whole charging scenario. Lower efficiency means more billed electricity is needed for the same stored energy.

Common mistakes to avoid

  • Do not subtract the loss percentage from the required stored energy.
  • Idle charges, parking charges and time-based tariffs need a separate amount or calculation.

Assumptions to check

  • Efficiency is a scenario assumption, not a guarantee for your charger. Time-based, idle and parking fees are not inferred.

Sources and method

Read our calculation and testing approach.