EV Charging Time Calculator

Electric vehicle charging cost depends on your car’s battery capacity, current state of charge, charging equipment level, your electricity rate, and charging efficiency losses. Understanding these variables helps you budget accurately and compare EV costs to gasoline.

Formulas:

Energy to Charge (kWh) = Battery Capacity × (Target% − Current%) ÷ 100
Actual Energy Drawn = Energy to Charge ÷ Charging Efficiency
Charging Cost = Actual Energy Drawn × Electricity Rate ($/kWh)
Cost per Mile = Charging Cost ÷ Miles Driven
Miles of Range Added = Energy to Charge × Vehicle Efficiency (miles/kWh)

Charging levels:

Charging efficiency losses: Level 1 and 2 are approximately 85–90% efficient (AC to DC conversion generates heat). DC fast charging: 85–95%. Onboard charger and battery chemistry also affect efficiency.

Average US electricity rates (2024): $0.12–$0.18/kWh residential. Peak vs. off-peak rates: off-peak (midnight–6 AM) can be $0.07–$0.10/kWh in many areas.

Worked example:

Tesla Model 3 (82 kWh battery, 4.0 miles/kWh efficiency). Currently at 20%, charging to 80% at home (Level 2). Electricity rate: $0.14/kWh. Charger efficiency: 88%.

Energy to charge = 82 × (80 − 20) ÷ 100 = 82 × 0.60 = 49.2 kWh
Actual energy drawn = 49.2 ÷ 0.88 = 55.9 kWh
Charging cost = 55.9 × $0.14 = $7.83
Miles of range added = 49.2 × 4.0 = 196.8 miles
Cost per mile = $7.83 ÷ 196.8 = $0.040/mile

Comparison to gasoline:

A 30 MPG gas car driving 196 miles uses 6.53 gallons × $3.50 = $22.87
EV cost: $7.83, a 66% saving on that trip.

Annual savings estimate: At 12,000 miles/year and $0.04/mile: EV cost = $480. Gas car at 30 MPG and $3.50/gallon: $1,400. Annual savings: $920.