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⚡ Charging time · Grid energy · Charging session cost
EV Charging Time & Cost Calculator
Estimate battery charging time, grid energy consumption, and charging cost for any electric vehicle based on charger power, efficiency, and electricity rates.
Step By Step
How to Use This Calculator
6 steps
- Enter your EV's battery capacity in kWh, or choose from popular electric vehicle presets.
- Select your charging power in kW, or select from charger presets (Level 1, Level 2, or DC Fast charging).
- Input your current battery level (Start %) and target battery level (Target %).
- Enter your local electricity rate per kWh (or utility slab cost).
- Choose your charging efficiency (standard AC charging is ~88%, DC fast charging is ~95% due to heat losses).
- Review the calculated charging duration, total charging cost, energy drawn from the grid, and range gained.
Worked Example
Example: Charging a 75 kWh battery from 20% to 80% on a 11 kW Level 2 charger at $0.15/kWh
Use this sample to sanity-check your inputs and understand what the final result represents.
- 1Battery energy needed = 75 kWh × (80% − 20%) ÷ 100 = 45 kWh.
- 2Grid energy drawn (at 88% efficiency) = 45 kWh ÷ 0.88 = 51.14 kWh.
- 3Charging time = 45 kWh ÷ (11 kW × 0.88 efficiency) = 4.65 hours (4 hours 39 minutes).
- 4Session charging cost = 51.14 kWh × $0.15 = $7.67.
Final Result
It will take 4 hours 39 minutes and cost $7.67 to add 60% charge, drawing 51.14 kWh from the power grid.
Methodology
EV Battery Charging Mathematics
This section explains the calculation logic, assumptions, and source material used to make the result more trustworthy and easier to verify.
Energy Stored in Battery (kWh) = Capacity (kWh) × (Target% − Start%) ÷ 100. Grid Energy Drawn (kWh) = Energy Stored ÷ Efficiency. Charging Duration (Hours) = Energy Stored ÷ (Charging Power kW × Efficiency). Charging Session Cost = Grid Energy Drawn × Electricity Rate per kWh. Estimated Range Added = Energy Stored × Vehicle Efficiency (km/kWh or miles/kWh). DC Fast Charger curves typically slow down power draw exponentially once the battery level crosses 80%.
Helpful tips
- 1Avoid charging past 80% on DC Fast Chargers. Charging speeds drop exponentially to prevent heat buildup and protect battery life.
- 2Charging is not 100% efficient. AC charging loses ~10%–15% of energy, which means your billing reflects more kWh than what is stored in the EV battery.
- 3Check your local utility rates. Charging your EV overnight during off-peak hours can lower charging bills by up to 50%.
- 4Onboard chargers limit maximum AC speed. If your EV's onboard charger is rated at 7.4 kW, charging on a 22 kW AC public charger will still be limited to 7.4 kW.
Frequently Asked Questions
What is the formula to calculate EV charging time?+
The charging time formula is: Charging Time (Hours) = (Target Battery % - Start Battery %) * Battery Capacity (kWh) / (100 * Charging Power kW * Charging Efficiency). For example, charging a 60 kWh battery from 10% to 80% on a 7 kW home charger at 88% efficiency takes: (70 * 60) / (100 * 7 * 0.88) = 4,200 / 616 ≈ 6.8 hours (6 hours 49 minutes).
What is EV charging efficiency and why does energy loss occur?+
Charging an electric vehicle involves AC-to-DC conversion (for AC chargers) and heat generation, resulting in energy loss. AC charging (Level 1 and Level 2) is typically 85-90% efficient (10-15% loss). DC Fast charging bypasses the vehicle's onboard charger and is more efficient, around 95% (5% loss). This means your electricity bill will reflect 5% to 15% more kWh than what is stored in the car's battery.
Why does DC Fast Charging speed slow down dramatically after 80%?+
Lithium-ion EV batteries charge in phases. Constant Current (CC) phase is fast, but once the battery reaches around 80% capacity, it switches to Constant Voltage (CV) phase. During CV, the battery management system (BMS) lowers charging power (kW) progressively to prevent overheating, cell degradation, and thermal runaway. Charging from 80% to 100% can often take as long as charging from 10% to 80%.
How is the cost of charging an electric vehicle calculated?+
To find the charging cost, calculate the total energy drawn from the grid (adding energy losses) and multiply it by your local electricity rate: Charging Cost = (Energy Needed in kWh / Charging Efficiency) * Electricity Rate per kWh. For instance, adding 50 kWh to a battery at 88% efficiency draws 56.8 kWh from the grid. At an electricity rate of ৳8.50/kWh, the cost is 56.8 * 8.50 ≈ ৳483.
How much driving range do I gain per hour of charging?+
Range gained depends on charging speed and your vehicle's energy efficiency (measured in km/kWh or miles/kWh). Range Gained per Hour = Charging Power (kW) * Charging Efficiency * EV Efficiency. For a mid-size EV with an efficiency of 6 km/kWh, a 7 kW home charger at 88% efficiency adds: 7 * 0.88 * 6 = 36.96 km of range per hour of charging.
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