Calcylator
EV Charging Cost

EV charging cost:
grid energy times your rate

See what a charge costs at a home tariff and at a public charger, how charging loss raises the bill, and what that means per kilometre.

Calcylator Editorial Team

Updated · 5 min read

How to calculate EV charging cost

EV charging cost is the energy drawn from the grid times your rate per kWh. To put 30 kWh into a battery with 10% charging loss, you draw 30 ÷ 0.90 = 33.33 kWh, which costs ₹266.67 at ₹8 per kWh.

EV charging cost =gridKwh = energyAdded ÷ (1 − loss ÷ 100), cost = gridKwh × rate
energyAdded:
kWh that ends up in the battery
loss:
charging loss in percent, from 0 to 30
rate:
price per kWh in rupees
gridKwh:
energy drawn from the grid
The loss slider starts at 10%. The tool shows both grid energy and cost in INR.

  • Energy added

    30 kWh

  • Charging loss

    10%

  • Rate

    ₹8 per kWh

Charging cost

₹266.67

Grid energy: 30 ÷ 0.90 = 33.33 kWh. Cost: 33.33 × 8 = ₹266.67.

You pay for the grid energy, not just the energy that reaches the battery, because some is lost as heat in the charger and the battery.

Home versus public charging

The same charge can cost very different amounts depending on where you plug in. A home tariff is often much lower than a public fast charger. The rates below are examples, not quotes, so use the price on your own bill or the charger's app.

Cost of adding 30 kWh, by rate and loss
Charging lossGrid energy (kWh)At ₹8 per kWhAt ₹18 per kWh
0%30₹240₹540
10%33.33₹266.67₹600
20%37.5₹300₹675
30%42.86₹342.86₹771.43

At an assumed 10% loss, charging 30 kWh costs ₹266.67 at ₹8 and ₹600 at ₹18, so the public charger costs 2.25 times as much. Many owners charge at home overnight and keep fast chargers for trips.

Turning a charge into cost per kilometre

Suppose the car uses 15 kWh per 100 km at the battery. At 10% loss and ₹8, that is 15 ÷ 0.90 = 16.67 kWh from the grid, ₹133.33 per 100 km, or about ₹1.33 per km. At ₹18 it is ₹300 per 100 km, or ₹3 per km.

Compare this with a petrol car: ₹105 a litre at 16 km/L is about ₹6.56 per km. Always compute both from your own numbers, since tariffs, mileage and efficiency vary.

Public chargers sometimes bill per minute or per session instead of per kWh. If that is the case, divide the total you paid by the kWh added to get an effective rate, then enter that rate in the calculator so you can compare it fairly with your home tariff.

Why there is a charging loss

Charging is not perfectly efficient. The charger converts alternating current to direct current, the battery warms up, and the car's own systems may run during the charge. The slider covers 0% to 30%, so you can test a low figure and a cautious one.

As a worked comparison, a 20% loss on the same 30 kWh needs 37.5 kWh from the grid, which costs ₹300 at ₹8. That is ₹33.33 more than at 10% loss, with the same energy reaching the battery.

If you do not know your loss, 10% is the default and a reasonable starting point. A higher loss raises the bill, as the table shows.

Common mistakes

  • Ignoring charging loss and paying for more energy than you budgeted.
  • Using the battery's full size when you only add part of it. Enter the kWh actually added.
  • Mixing kW (power) with kWh (energy). A 7 kW charger running one hour adds up to 7 kWh before losses.
  • Assuming a public rate equals your home rate.
  • Forgetting extra fees such as parking or idle charges at some public chargers.

Common questions

How do I calculate EV charging cost?

Divide the energy added to the battery by 1 minus the loss as a fraction to get grid kWh, then multiply by your rate. For 30 kWh, 10% loss and ₹8 per kWh, the cost is 33.33 × 8 = ₹266.67.

Is home charging cheaper than public charging?

Usually yes, because home tariffs are often lower than public fast charger prices. At example rates of ₹8 and ₹18 per kWh, adding 30 kWh with 10% loss costs ₹266.67 at home and ₹600 at a public charger.

What is charging loss?

Charging loss is the share of grid energy that never reaches the battery, lost mainly as heat in the charger and battery. With a 10% loss, 33.33 kWh drawn from the grid leaves 30 kWh in the battery.

How much does it cost to charge per 100 km?

Multiply the car's kWh per 100 km by the rate and divide by 1 minus the loss. For 15 kWh, ₹8 and 10% loss, that is ₹133.33 per 100 km. At ₹18 per kWh it rises to ₹300.

What charging loss should I enter?

The Calcylator slider starts at 10%, which is a sensible default, and runs from 0% to 30%. Try a few values to see the effect. If you have your own meter readings, compare grid kWh with the battery energy to find your real loss.

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