How it works
Usable capacity is the energy the driver can actually use, which is often a bit less than the advertised pack size. Enter the starting and target charge as percentages from 0 to 100, with the target no lower than the start. Charging efficiency is the energy that reaches the battery divided by the energy pulled from the grid, so at 90% the wall supplies more than the battery receives.
Match the unit price to whatever your tariff or receipt actually bills. A home tariff measured at the wall uses grid energy. Choose battery energy only when that's truly what you're billed for, and check with the provider, since public chargers measure in different places. Charging time uses average grid input power; it isn't a prediction of the real charging curve.
The formula behind the estimate
Every result starts with a defined model and visible assumptions.
Battery energy added = usable capacity × (target charge − starting charge) ÷ 100 Grid energy = battery energy added ÷ (charging efficiency ÷ 100) Billed energy = grid energy OR battery energy, using your selected tariff boundary Session cost = billed energy × unit price + flat session fee Time = grid energy ÷ average grid input power
A worked example
A 60 kWh usable battery charged from 20% to 80% gains 36 kWh. At 90% efficiency the grid supplies 40 kWh, and at 0.20 per kWh with no session fee the cost is 8.00 in your chosen currency. At an average input of 7.2 kW, that's about 5.56 hours. The inputs are illustrative, not real electricity prices or a test of any particular car.
How do home and public charging costs differ?
The price field takes an amount per kWh in your currency, and the flat session fee is added once per session. It isn't a monthly subscription or a per-minute rate. Include any per-kWh taxes in the price and any fixed transaction charge in the session fee. If a time-of-use rate changes partway through a session, run the calculation separately for each part.
What's the difference between kW and kWh?
kWh is an amount of energy, while kW is how fast it moves. Dividing the grid energy you need by your average power gives hours. A charger's advertised peak power isn't held for the whole session, because the car's limits, charging taper, temperature and equipment all affect the real time. Efficiency is an assumption too, not a fixed property of a charger.
Can I compare costs in one currency?
Yes. Choose USD, PKR, INR, GBP, CAD, AUD, AED or EUR and enter all prices in that currency. The selection doesn't convert anything or supply a national tariff, and the source links cover US charging basics only. For a petrol or diesel budget use the fuel cost calculator; this tool estimates one charging session, not a full EV-versus-gas comparison.
Questions worth asking
Does this include charging losses?
Yes. Grid energy is the battery energy divided by your charging efficiency. Set the efficiency to match your equipment, and match the unit price to what your tariff actually bills.
Should I use the advertised battery capacity?
Use usable capacity when you can find it. Total pack size and usable capacity often differ, and that changes how much energy a charge really adds.
Is the time result a guaranteed charging time?
No. It assumes your average grid input power stays exactly as entered. Charging taper, temperature and the charger itself can all change the real duration.
Are public charging fees included?
Only the unit price and the one flat session fee you enter. Subscriptions, idle charges, parking, per-minute billing and installation costs are left out.
Does this find electricity prices in my country?
No. The currency setting only affects how amounts are displayed. Enter your local tariff and confirm where the energy is metered.
This is general information, not personalized financial advice. Read the limitations.
