What the animation shows
The animation and the step-by-step video above use your numbers. Here is the same walkthrough written out for the default example.
What you enter
- Usable battery capacity: 75 kWh.
- Starting charge: 20 %.
- Target charge: 80 %.
- Charging efficiency: 90 %. Level 2 home charging is often 85–95% efficient.
- Charging power: 7.6 kW.
- Electricity rate: 0.15 $/kWh. Find this on your utility bill: total charges ÷ kWh used gives an all-in rate.
What happens, step by step
- The 7.6 kW charger fills the battery from 20% to 80%.
- Some power warms the cable and charger, so the grid supplies 50 kWh.
- Charging takes 6.6 hours and costs $7.50 at $0.15/kWh.
The answer: charging cost is $7.50.
How it’s calculated
- Energy added = capacity × (target − start)
- Grid energy = added ÷ efficiency
- Time = grid energy ÷ charger power
Worked example
75 kWh battery from 20% to 80% on a 7.6 kW charger, 90% efficiency, $0.15/kWh.
Inputs
- Usable battery capacity
- 75 kWh
- Starting charge
- 20 %
- Target charge
- 80 %
- Charging efficiency
- 90 %
- Charging power
- 7.6 kW
- Electricity rate
- 0.15 $/kWh
Results
- Charging cost
- $7.50
- Charging time
- 6.6 hours
- Energy from the grid
- 50 kWh
- Energy added to battery
- 45 kWh
Assumptions and limits
- Charging power is constant. DC fast charging tapers above roughly 80%, so this does not apply to fast chargers.
- The car accepts the full charger power.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
How much does it cost to charge an EV at home?
Adding 45 kWh at 90% efficiency and $0.15/kWh costs about $7.50. Your rate, especially off-peak rates, makes the biggest difference.
How long does Level 2 charging take?
Divide the energy from the grid by the charging power. 50 kWh at 7.6 kW takes about 6.6 hours.