This calculator finds the energy needed to go from your current charge level to your target percentage, then divides by your charger’s effective power output to estimate charging time.
Tesla Charge Time Calculator
Estimated EV charge time, from battery capacity, the charge percentage needed, and charger power.
What the Tesla Charge Time Calculator Covers
This calculator covers EV charge time estimates based on battery capacity, current and target charge percentage, charger power, and charging efficiency — useful for planning a home charging session, estimating overnight charge time, or comparing charger power levels.
This estimate works best for AC (Level 1/2) home charging in the roughly 20–80% range, where charging speed stays relatively constant. It’s a less accurate model for DC fast charging, where charge speed typically tapers significantly as the battery approaches full.
How Charge Time Is Calculated
Formula
Charge Time = Battery Capacity × (Target % − Current %) ÷ 100 ÷ (Charger Power × Efficiency ÷ 100)
Where:
- Battery Capacity = the vehicle’s total battery capacity in kWh
- Current % / Target % = your battery’s current charge level and desired target level
- Charger Power = your charger’s rated power output in kW
- Efficiency = charging efficiency, since some energy is lost as heat during charging (commonly cited around 85–90% for AC home charging)
Worked Example
A 75 kWh battery, charging from 20% to 80%, on an 11 kW charger at 90% efficiency.
Energy Needed = 75 × (80 − 20) ÷ 100 = 75 × 0.6 = 45 kWh
Effective Charger Power = 11 × 0.9 = 9.9 kW
Charge Time = 45 ÷ 9.9 ≈ 4.55 hours
Charging this battery from 20% to 80% on an 11 kW home charger would take roughly 4.5 to 4.6 hours at this efficiency.
Why DC Fast Charging Doesn’t Fit This Model as Well
DC fast chargers typically deliver their fastest charging speed at lower battery percentages and taper off considerably as the battery approaches full, to protect battery health. This calculator assumes a roughly constant charge rate, so it’s most accurate for AC charging and less accurate for a full DC fast-charge session, especially past 80%.
Frequently Asked Questions
Why isn’t my actual charge time matching this estimate?
Actual charging speed can be affected by battery temperature, the vehicle’s own charge-rate limiting, and whether you’re on AC or DC charging — this calculator assumes a constant rate, which is a simplification of real-world tapering behavior.
What charging efficiency should I use for a home Level 2 charger?
A commonly cited range for AC home charging efficiency is roughly 85–90%, accounting for energy lost as heat during the AC-to-DC conversion process inside the vehicle.
Should I calculate charge time to 100% or to 80%?
Many EV manufacturers recommend regularly charging to around 80% rather than 100% for daily use, both because charging slows significantly near full and for long-term battery health reasons, so calculating to 80% often better reflects a realistic home charging routine.
Does a higher-power charger always charge faster?
Only up to the point where the vehicle’s onboard charger or battery can accept that power — if your charger’s output exceeds what your vehicle can actually draw, the vehicle’s own limit, not the charger’s rated power, will determine the real charging speed.
