How This Calculation Works
Charging cost equals the energy needed (kWh) multiplied by your electricity rate ($/kWh). The energy needed depends on your battery size and how much charge you are adding (target % minus current %).
Charging time depends on the charger power (kW). Level 1 (120V) provides ~1.4 kW, Level 2 (240V) provides 3–19 kW, and DC fast chargers provide 50–350 kW.
Common Mistakes to Avoid
- Ignoring charging losses. About 10–15% of energy is lost as heat during charging. Your actual cost is slightly higher than the raw calculation.
- Comparing home vs public costs. Home charging at $0.12/kWh costs ~$4 for a full charge. DC fast chargers at $0.40/kWh cost ~$30 for the same charge.
- Charging to 100% regularly. Most EV manufacturers recommend charging to 80% for daily use to preserve battery longevity.
Worked Example
Scenario: 75 kWh battery, charging from 20% to 80% at home ($0.14/kWh) with a 7.4 kW Level 2 charger.
Energy needed: 75 × (80 − 20)/100 = 45 kWh.
Cost: 45 × $0.14 = $6.30.
Time: 45 ÷ 7.4 = 6.1 hours.