EV Charge Cost at the Meter
What one EV charge costs on the utility meter, not the dashboard: you pay for kWh at the meter, not at the battery.
Example
You enter
- Battery capacity (kWh) 75
- Start state of charge (%) 20
- Target state of charge (%) 80
- Electricity rate ($/kWh) 0.15
- Charging efficiency (%) 88
- Vehicle efficiency at the battery (mi/kWh, 0 = skip; an EPA sticker figure is wall-based, so set charging efficiency to 100% with it) 3.5
You get
- Energy to battery 45 kWh
- Grid energy (metered) 51.1 kWh
- Cost $7.67
- Cost per stored kWh $0.171
- Cost per mile 0.0487
Checked against published worked examples from: US DOE Alternative Fuels Data Center.
Details, formula, and sources
ScopeEnergy to the pack = capacity x (target - start); the meter draws more because AC Level 2 loses about 10-15% to the onboard rectifier and thermal load, so grid energy = battery energy / efficiency. A 75 kWh EV, 20 to 80% (45 kWh) at $0.15/kWh and 88% efficiency draws 51.1 kWh and costs $7.67 -- not the $6.75 the dashboard math implies -- an effective $0.170/kWh, and about $0.049/mi at 3.5 mi/kWh. A public DC fast charger at $0.45/kWh runs nearly 3x that. Ignores tiered, time-of-use, and demand pricing; the local tariff governs.
Formula or tableenergy_to_battery = capacity x (target - start)/100; grid_energy = energy_to_battery / (efficiency/100); cost = grid_energy x rate; cost_per_stored_kwh = rate / (efficiency/100); cost_per_mile = miles_per_kwh > 0 ? cost / (energy_to_battery x miles_per_kwh) : null.
Source and editionEV charge-cost-at-the-meter model (energy metered = energy stored / charging efficiency), first-principles; the local tariff and the vehicle's charging behavior govern the actual bill.
Free accessCost = metered energy x rate is first-principles; the efficiency haircut (grid draws more than the pack stores) is inherent to AC charging losses, and the rate comes from the local tariff.
What governsEstimate. AHJ and licensed professional govern.
API field namesbattery_capacity_kwh, start_soc_pct, target_soc_pct, electricity_rate, efficiency_pct, miles_per_kwh, energy_to_battery_kwh, grid_energy_kwh, cost, cost_per_stored_kwh, cost_per_mile
- Metered energy grid draws more than the battery stores: grid_energy = battery_energy / efficiency (default 88%)AC charging losses
- Flat rate constant $/kWh; ignores tiered, time-of-use, and demand pricingscope of this tile
- Currency rate, cost, cost per kWh, and cost per mile carried as dimensionless; currency and mileage are not physical dimensionscost-tile convention