EV Charging Cost Calculator

About this calculator

The energy that ends up in the battery is not the energy the meter counts. Charging loses something to heat in the charger, the cable and the cells, so a 30 kWh charge pulls around 35 kWh through the socket — and it is the socket figure you pay for.

This page works out both, from your battery, your charge window and your own tariff. Add the efficiency your car reports and it will also tell you what the charge costs per kilometre.

How to use this calculator

1. Enter the usable battery capacity in kWh, from the handbook.
2. Set the starting and target percentages. 20–80% is the usual fast-charging window.
3. Enter the electricity rate you pay — your own domestic tariff, or the price shown on a public charger.
4. Optionally add your efficiency in km/kWh to see the range the charge buys.
5. Leave charging efficiency blank to use this page's 85% assumption, which the result names.

The formula

Energy into battery = Capacity x (Target - Start) / 100
Energy from supply  = Energy into battery / Charging efficiency
Cost                = Energy from supply x Rate per unit
Range added         = Energy into battery x Efficiency (km/kWh)

The charging efficiency is an assumption and is named as one. Eighty-five per cent is a reasonable starting point for AC charging; a DC fast charge is often better at the car end and worse at the grid end, and the honest answer is that it varies.

Worked example

A 30 kWh battery from 20% to 80% at ₹8 a unit, 85% charging efficiency:

Into battery = 30 x 0.60       = 18 kWh
From supply  = 18 / 0.85       = 21.18 kWh
Cost         = 21.18 x 8       = 169.41

At 6 km/kWh that 18 kWh is 108 km of range, so ₹1.57 a kilometre — about a fifth of what a petrol hatchback costs to cover the same ground.

Notes and limits

• Usable capacity is a little below the gross figure a manufacturer quotes, because a buffer is held at each end to protect the cells. Use the usable number if you have it.
• Public fast charging commonly costs several times a domestic tariff, and some networks add a session fee or an idle fee. Neither is included unless you add it.
• Charging to 100% regularly is harder on a lithium battery than stopping at 80%, which is why 80% is the default here.
• Slab tariffs mean the marginal unit can cost more than your average unit. Charging at home may push you into a higher slab — check the bill rather than the headline rate.
• The EV charging time calculator answers the other half of the question.

What this calculation assumes

• Charging efficiency defaults to 85% and is named in the result. It is an assumption, not a specification.
• Battery capacity, tariff and efficiency are figures you entered. No vehicle data is stored here.
• Session fees, idle fees and tariff slabs are not included unless you fold them into the rate.