Ownership tool
EV charging time calculator
Enter battery size, current and target charge and stall power to estimate charge time, energy added and the cost — with a note when the taper above 80% stretches the real duration.
Estimated charge time
4 h 33 min
This session adds 45.0 kWh and costs about $9.
| Energy into the pack | 45.0 kWh |
|---|---|
| Energy drawn from the grid | 50.0 kWh |
| Estimated cost | $9 |
| Effective charge rate | 9.9 kW |
Above 80% the BMS tapers power sharply — DC sessions can slow to a third of peak, so real-world time often runs 10–30% longer.
How it is calculated
Charge time = battery capacity × (target − current charge) ÷ (stall power × efficiency). Energy added is pack-side; cost is billed on grid-side energy, which is the pack figure divided by efficiency.
The estimate holds power constant. Above about 80% the battery management system tapers the rate, and cold packs warm up first — real sessions usually run longer.
Use the lower of the car's charge limit and the stall's rating: an 11kW stall feeds a 7.7kW on-board charger at only 7.7kW.
How to fill each field
- Battery capacityUse the usable pack size of your trim. An approximation is fine — the error scales linearly with capacity.
- Charger powerLevel 2 home chargers deliver 7.7–11.5kW; public DC stalls run 50–350kW. Enter the stall rating, not the car's peak.
- EfficiencyLosses come from the on-board charger, cabling and cell resistance. AC is typically 85–92%, DC 90–95%; leave 90% when unsure.
FAQ
How long does a 75kWh pack take on an 11kW home charger?
20%→80% is about 4.2 hours: 45kWh into the pack, divided by 11kW at 90% efficiency. A 10%→100% overnight charge runs about 6.8 hours.
Why does a real session take longer than the estimate?
The estimate holds power constant. Above ~80% the BMS tapers the rate — DC sessions can slow to a third of peak — and a cold pack preheats before ramping. Budget an extra 10–30% at the top end.
Do I enter the car's peak or the stall's rating?
Enter whichever is lower in practice. A car capped at 60kW draws 60kW on a 120kW stall; a car with a 7.7kW on-board charger pulls 7.7kW from an 11kW AC post.
What is the 90% efficiency figure?
Energy is lost between the meter and the pack — on-board charger conversion, cable losses and cell resistance — roughly 8–15% combined. Billing is on grid energy, so the pack figure is divided by efficiency.
How much longer is 100% than 80%?
At constant power it is just 20% more energy. In practice the 80–100% segment slows sharply and can take as long as the whole 20–80% window — stop at 80–90% daily and charge to full only before trips.