How we calculate EV charging cost

Every number on the charging cost calculator comes from a few simple formulas. Here they are, with the default values we use and why.

1. Energy you pay for

Energy (kWh) = battery capacity × (target % − current %) ÷ 100 ÷ charging efficiency

Not all the electricity from the socket ends up in the battery. Some is lost as heat in the charger, cables and battery. We assume 90% efficiency for AC charging (home and public AC) and 93% for DC fast charging. You can change both under “Advanced”. One kWh is one “unit” on your electricity bill.

2. Cost of this charge

Cost = energy × electricity rate (₹ per unit)

Default rates, which you should replace with your own:

• Home: ₹8 per unit, a typical domestic tariff including taxes.
• Public AC charger: ₹12 per unit.
• Public DC fast charger: ₹18 per unit.

Tariffs vary by state, electricity board, slab and charging network, so treat these as starting points.

3. Cost per km

Cost per km = (battery capacity × rate ÷ efficiency) ÷ real-world range

We use real-world range, not the claimed (IDC, ARAI or MIDC) figure, because test-cycle ranges are usually higher than what riders and drivers see. Where we couldn't find a sourced real-world figure, we use 75% of the claimed range and say so on the model page. With a custom vehicle, you enter the range yourself.

4. Full charge and monthly cost

Full charge is the same formula from 0% to 100%. Monthly cost = cost per km × daily km ×30. It only appears when you enter a daily distance.

5. Petrol comparison

Petrol cost per km = petrol price ÷ mileage. We default to ₹105 a litre and typical mileages of 45 km/l for 2-wheelers, 25 km/l for 3-wheelers and 15 km/l for cars. Savings are the petrol cost minus the charging cost for the same distance; yearly savings are 12 × monthly.

Worked example

A car with a 30 kWh battery and 250 km real-world range, charged from 20% to 80% at home at ₹8 per unit:

• Energy: 30 × 60 ÷ 100 ÷ 0.9 = 20 kWh
• Cost of the charge: 20 × ₹8 = ₹160
• Cost per km: (30 × 8 ÷ 0.9) ÷ 250 = ₹1.07

What we don't include

• Fixed charges, parking or idle fees, and GST changes on your bill or at the charger.
• Cold weather, air-conditioning, heavy loads, highway speeds and hills, which all reduce range.
• Battery ageing, which slowly reduces capacity and range.

Results are estimates. Actual costs vary with your tariff, charger losses, temperature and driving style. Vehicle specs come from manufacturer and published sources; each model page lists its sources and when we last checked them.