- 1Enter total Electric Vehicle battery pack capacity in kWh (e.g. 75 kWh).
- 2Enter electricity price in dollars per kWh ($ / kWh).
- 3Enter starting state of charge percentage (Start %, e.g. 20%).
- 4Enter target state of charge percentage (Target %, e.g. 80%).
- 5Enter charger efficiency percentage (defaults to 90%).
- 6View total charging session cost ($) and gross energy drawn from grid (kWh).
Electric vehicle charging costs depend on battery capacity, state of charge (SOC) added during the session, electricity rates, and charger efficiency losses during energy transfer.
Net kWh stored in battery pack.
Net kWh = Battery Capacity (kWh) × [ (Target % − Start %) / 100 ]Accounts for charger conversion efficiency loss (default 90%).
Gross kWh = Net kWh / (Charger Efficiency % / 100)Multiplies gross electricity drawn by rate per kWh.
Total Cost ($) = Gross kWh × Electricity Price ($ / kWh)Added Charge = 80% − 20% = +60%
Net kWh = 75 × 0.60 = 45.0 kWh
Gross kWh Drawn = 45.0 / 0.90 = 50.0 kWh
Total Cost = 50.0 × $0.16 = $8.00Net kWh = 60 × 60/100 = 36; Gross kWh = 36 / 0.90 = 40; Cost = 40 × 0.15Net kWh = 80 × 90/100 = 72; Gross kWh = 72 / 0.85 ≈ 84.7; Cost ≈ 84.7 × 0.30- Charger efficiency factor: Defaults to 90% to model typical AC Level 2 and DC fast-charger thermal/conversion losses (10% lost as heat).
- Target vs Start constraint: Target SOC must be strictly greater than Start SOC (Target % > Start %).
- Unmodeled elements: Models energy cost only. Charging speed (kW power) and DC fast-charging thermal power tapering curves above 80% SOC are not modelled.
Why does charging cost more than the net energy added to the battery?
Because no charging system is 100% efficient. Energy is lost as heat during AC-to-DC conversion and battery thermal management (modelled here at 90% efficiency).
Why is 80% state of charge a common target?
Charging above 80% slows down significantly on fast chargers to protect battery health. Charging from 20% to 80% is the most time- and cost-efficient range.
What does charging efficiency represent?
The share of drawn energy that actually reaches the battery. The calculator divides the net energy added by the efficiency fraction to get the gross energy you pay for.
Why must the target charge be above the current charge?
The calculation only covers adding charge; if the target is not higher than the current level there is nothing to compute and it returns no result.
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