Home Charging Time Estimator

Estimate how long it will take to fully charge your electric vehicle at home based on your charger type, battery size, and current charge level.

Total usable battery capacity of your EV (check your owner's manual or manufacturer specs).
How charged is your battery right now? (0–99%)
What charge level do you want to reach? (1–100%; 80% recommended for daily use to preserve battery health)
Your EV's on-board charger may accept less power than your EVSE provides. Leave blank if unknown (we'll use the EVSE power). Common values: 3.3, 6.6, 7.2, 11, 22 kW.
AC-to-battery charging efficiency (typically 85–95%). Default: 90%.

Formula

Step 1 – Energy needed in battery (kWh):
Ebattery = Battery Capacity (kWh) × (Target SOC% − Current SOC%) / 100

Step 2 – Energy drawn from the wall (kWh):
Ewall = Ebattery / Charging Efficiency
Accounts for heat losses in the on-board charger and wiring.

Step 3 – Effective charger power (kW):
Peff = min(EVSE Power, OBC Limit)
The actual charging rate is limited by whichever is lower: your wall charger or your vehicle's on-board charger.

Step 4 – Charging time (hours):
Time (hrs) = Ewall / Peff

EVSE Power: P (kW) = Voltage (V) × Amperage (A) / 1000

Assumptions & References

  • Charging efficiency of 85–95% is typical for modern EVs; default is 90% (SAE J1772 standard losses).
  • Level 1 charging uses a standard 120V household outlet (NEMA 5-15 or 5-20); Level 2 uses a 240V circuit (NEMA 14-50 or hardwired EVSE).
  • EVSE power = Voltage × Amperage. NEC 80% continuous load rule means a 40A breaker supports a 32A EVSE (7.68 kW).
  • The on-board charger (OBC) inside the vehicle converts AC power to DC for the battery. Common OBC limits: 3.3 kW (older EVs), 6.6–7.2 kW (most modern EVs), 11–22 kW (some European models).
  • Charging slows (tapers) near 100% SOC due to battery management system (BMS) protection — actual time near full charge may be longer than estimated.
  • Electricity cost estimate uses the U.S. average residential rate of ~$0.16/kWh (U.S. EIA, 2024). Your rate will vary.
  • Battery capacity used is usable capacity (manufacturers typically reserve 5–10% as a buffer not accessible to the driver).
  • References: SAE J1772 (EV charging standard), U.S. DOE Alternative Fuels Data Center (afdc.energy.gov), NEC Article 625 (EV charging equipment), U.S. EIA Electric Power Monthly.

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