Charging Time Calculator by Charger Level and Battery Size
Estimate how long it will take to charge your electric vehicle based on your charger type, battery capacity, and current state of charge.
Typical AC charging: 85–92%. DC fast charging: 90–95%.
Formula
Step 1 — Energy Needed (kWh):
Energy = 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)
Example: 75 kWh battery, 20% → 80% SOC, 6.6 kW charger, 90% efficiency:
Energy = 75 × (80−20)/100 = 45 kWh | Effective Power = 6.6 × 0.90 = 5.94 kW | Time = 45 ÷ 5.94 ≈ 7.58 hrs (7 hr 35 min)
Assumptions & References
- Charging efficiency accounts for heat loss and power conversion losses in the onboard charger (OBC). AC Level 1/2 typical efficiency: 85–92%; DC fast charging: 90–95% (SAE J1772).
- Level 1 chargers use a standard 120V household outlet (NEMA 5-15 or 5-20). Level 2 chargers use 240V (NEMA 14-50 or hardwired). DC fast chargers bypass the OBC entirely.
- Battery capacity shown is usable capacity. Some manufacturers report gross capacity; usable is typically 90–95% of gross.
- Most manufacturers recommend charging to 80% for daily use to preserve battery longevity (per Tesla, GM, and Nissan owner guidelines).
- Range estimate uses a general average of 3.5 miles/kWh. Actual range varies by vehicle, speed, temperature, and driving style (EPA range estimates).
- Electricity cost estimate uses the U.S. average residential rate of $0.16/kWh (U.S. EIA, 2024). Rates vary significantly by region.
- DC fast charging speed may taper as the battery approaches 80% SOC to protect battery health; this calculator assumes constant power delivery.
- References: SAE J1772 standard, U.S. Department of Energy Alternative Fuels Data Center (afdc.energy.gov), U.S. EIA Electric Power Monthly.