What Is EV Charge Time?
EV charge time is how long it takes to move a given amount of electrical energy into an electric car's battery. Two things control it: how much energy the battery still needs, measured in kilowatt-hours (kWh), and how fast the charger can deliver energy, measured in kilowatts (kW).
A useful way to remember the relationship: kWh is the size of the job, kW is the speed of the worker. A big battery on a weak charger takes all night; the same battery on a 150 kW fast charger is done before your coffee cools.
The Charge Time Formula
The calculation is one division, with two adjustments — for how full the battery already is, and for the energy lost during charging:
[
\text{Charge Time} = \frac{\text{Capacity} \times \dfrac{\text{Target} - \text{Current}}{100}}{\text{Power} \times \dfrac{\text{Efficiency}}{100}}
]
Where:
- Capacity is the usable battery capacity in kWh.
- Current and Target are the starting and ending state of charge in percent.
- Power is the charger's output in kW.
- Efficiency accounts for charging losses — typically around 90%.
Because kWh ÷ kW leaves exactly hours, the units cancel cleanly: divide kilowatt-hours by kilowatts and the answer is always in hours.
Worked Example: Overnight Home Charging
A driver gets home with a 64 kWh battery sitting at 20%, plugs into a 7.4 kW home wallbox, and wants to leave at 80%. Assume a typical 90% charging efficiency:
[
\text{Energy Needed} = 64 \times \frac{80 - 20}{100} = 64 \times 0.6 = 38.4 \text{ kWh}
]
[
\text{Effective Power} = 7.4 \times 0.9 = 6.66 \text{ kW}
]
[
\text{Charge Time} = \frac{38.4}{6.66} \approx 5.77 \text{ hours} \approx 5 \text{ h } 46 \text{ min}
]
As a sanity check from the other side: drawing 38.4 ÷ 0.9 ≈ 42.7 kWh from the grid at 7.4 kW gives 42.7 ÷ 7.4 ≈ 5.77 hours too. Both routes agree, which is a good habit whenever you check any physics-style calculation.
Try It Yourself
Suppose a 75 kWh EV is at 40% and you plug it into an 11 kW wallbox, again at 90% efficiency. The battery only needs the top 40 points: 75 × 0.4 = 30 kWh. The effective power is 11 × 0.9 = 9.9 kW, so the time is 30 ÷ 9.9 ≈ 3.03 hours, or about 3 h 2 min. Run the same numbers through the calculator above to confirm.
Typical Charging Times by Charger Type
Charger power dominates everything else. These figures assume a full 0-to-100% charge of a 64 kWh usable battery at 90% efficiency:
| Charger | Power | Full charge time |
|---|---|---|
| Domestic socket | 2.3 kW | ≈ 31 hours |
| Home wallbox (single-phase) | 7.4 kW | ≈ 9.6 hours |
| Home wallbox (three-phase) | 11 kW | ≈ 6.5 hours |
| Public Level 2 | 22 kW | ≈ 3.2 hours |
| DC fast charger | 50 kW | ≈ 1.4 hours |
| DC ultra-fast charger | 150 kW | ≈ 28 minutes |
Two lessons fall out of this table. First, a domestic socket is fine overnight but painfully slow for anything urgent. Second, doubling the power halves the time — but only up to the limit your car's onboard hardware accepts, so a 350 kW charger won't help a car capped at 50 kW.
Quick Recap
- Charge time = energy needed ÷ effective charging power, where effective power is the charger's kW multiplied by efficiency.
- Only the energy between your current and target percentages counts — a 20%-to-80% session on a 64 kWh battery moves just 38.4 kWh.
- Real sessions run longer than the ideal math because of the charging taper near full and cold-battery slowdowns.
- Use the calculator above for any combination of battery, charge window and charger.
Once you know how long a charge takes, the natural companion question is how far that energy will carry you — the distance to empty (DTE) calculator covers exactly that.