EV Charging Time Calculator by Battery Size and Charger Level
Estimate how long it will take to charge your electric vehicle based on your battery size, current state of charge, target charge level, and charger type.
Total usable battery capacity of your EV (e.g. Tesla Model 3 Long Range = 75 kWh)
Your battery's current charge level (0–99%)
Desired charge level when done (1–100%)
Accounts for energy lost as heat during charging (typically 85–95%)
Formula
Step 1 – Energy Needed (kWh):
Energy Needed = Battery Capacity (kWh) × (Target SOC% − Current SOC%) ÷ 100
Step 2 – Effective Charging Power (kW):
Effective Power = Charger Power (kW) × (Efficiency ÷ 100)
Step 3 – Charging Time (hours):
Charging Time = Energy Needed (kWh) ÷ Effective Power (kW)
Step 4 – Grid Energy Drawn (kWh):
Grid Energy = Energy Needed ÷ (Efficiency ÷ 100)
Example: 75 kWh battery, 20% → 80% charge, 7.2 kW Level 2 charger, 90% efficiency:
Energy = 75 × 0.60 = 45 kWh | Effective Power = 7.2 × 0.90 = 6.48 kW | Time = 45 ÷ 6.48 ≈ 6 hours 56 minutes
Assumptions & References
- Charging time assumes constant power delivery throughout the session. In practice, DC fast chargers taper speed above ~80% SOC.
- Level 1 chargers use a standard 120V household outlet (~1.4 kW) or 240V NEMA 6-15 (~1.9 kW).
- Level 2 chargers use 240V AC and range from 3.3 kW (basic) to 19.2 kW (max J1772 at 80A).
- DC Fast Chargers (Level 3) bypass the onboard charger and deliver DC directly to the battery (50–350+ kW).
- Default charging efficiency of 90% accounts for heat losses in the charger, cables, and battery management system. Real-world values range from 85–95% depending on charger quality and ambient temperature.
- Battery capacity entered should be the usable capacity, not gross capacity. Many manufacturers list gross capacity; usable is typically 90–95% of gross.
- Cold weather can reduce charging speed and battery acceptance rate by 10–40%.
- References: SAE J1772 standard, U.S. Department of Energy Alternative Fuels Data Center (afdc.energy.gov), IEC 62196 (Type 2 connector standard).