EV Charging Cost Calculator

How to use the EV charging cost calculator

1. Under Battery and charger, enter the Usable battery capacity (kWh), the Start charge (%) and the Target charge (%).
2. Pick a Charger type (a 120 V outlet, a Level 2 home charger, a DC fast charger) or type your own Charger power (kW). Adjust the Charging losses (%) if you know them; 10% is a sensible default for home charging.
3. Under Electricity prices, enter your Home rate (per kWh). To compare with a public station, add the Public charger price (optional), choose per kWh or per minute, and any Session fee (optional).
4. Under Consumption and gasoline comparison, enter the EV consumption in kWh/100 km, kWh/100 mi, km/kWh or mi/kWh, and optionally a Gasoline car fuel economy (L/100 km, mpg US or UK, km/L) with the Gasoline price per litre or gallon.

The tool shows the Energy added to the battery, the Energy drawn from the grid, the Estimated charging time, the Cost at home, the Cost at the public charger, the Range added, the cost per 100 km and per 100 miles, the cost of the same distance with gasoline and what you save. Every step of the calculation is listed below the results. Any currency works.

The formulas

• Energy added (kWh) = capacity × (target % − start %)
• Energy from the grid = energy added ÷ (1 − losses). With 10% losses, putting 36 kWh in the battery takes 40 kWh from the outlet.
• Cost at home = grid kWh × rate per kWh
• Public cost = grid kWh × price per kWh, or minutes × price per minute, plus the session fee
• Range added = energy added ÷ consumption × 100
• Gasoline cost for the same distance = km × L/100 km ÷ 100 × price per litre

Example. A 60 kWh battery charged from 20% to 80% gets 36 kWh, or 40 kWh from the grid. At 0.15 per kWh the charge costs 6.00. At a public station billing 0.45 per kWh, the same charge costs 18.00. With a consumption of 17 kWh/100 km, it adds about 212 km (132 miles), so home charging costs 2.83 per 100 km. A gasoline car using 7.5 L/100 km at 1.65 per litre spends 12.38 per 100 km, or 26.21 for the same 212 km: 20.21 more.

How the charging time is estimated

The power that reaches the battery is the charger power minus the losses: 7.2 kW × 0.9 = 6.48 kW. Lithium-ion batteries charge at close to full speed up to about 80%, then the car tapers the current to protect the cells. This tool uses a simplified model: full power up to 80%, then half power above 80%. The example above (20% to 80% on 7.2 kW) takes about 5 h 33 min; going to 100% would add 12 kWh at 3.24 kW, about 3 h 42 min more. On a 50 kW DC charger, 20% to 80% takes about 48 minutes.

Real times vary: many cars accept only 7 to 11 kW on AC whatever the station offers, fast charging slows down in the cold, and the taper curve differs from one model to another.

Which consumption and loss figures to use

Enter the consumption shown by the car’s trip computer, which is measured at the battery. Official label figures (EPA in the US, WLTP in Europe) are measured at the outlet and already include charging losses: if you use them, set Charging losses (%) to 0 so they are not counted twice.