How this EV charging cost calculator works
Most “EV charging cost” tools multiply battery size by one electricity price. That misses the two things that move the real number most: where you charge and how much energy is lost on the way into the battery. A driver who charges overnight at home and one who lives on motorway fast chargers can pay a threefold difference for exactly the same car and mileage.
This calculator starts from your car’s real-world consumption (kWh per 100 km, as shown on the dashboard) and your monthly distance. It then splits your charging into three channels (home, public AC and DC fast), each with its own price and its own loss factor. Home charging can use an off-peak EV tariff and, optionally, your own solar electricity, which is valued at the export price you give up rather than at zero. The result is a blended cost per 100 km, per month and per year, the cost of a typical top-up and of a full charge, and a direct comparison with a petrol car.
The formula
Cost per 100 km (method i) = consumption × 1/(1 − loss_i) × price_i
Blended cost per 100 km = Σ share_i × cost per 100 km_i
Monthly cost = blended cost per 100 km × km ÷ 100 + subscriptions Home price with solar = solar share × export price + (1 − solar share) × grid price
Losses default to 10% for home and public AC and 5% for DC, because DC chargers meter the energy at the charger output, so you only pay for the small losses inside the car.
Worked example
The defaults describe a mid-size EV with a 60 kWh usable battery using 17 kWh/100 km and driving 1,250 km a month (15,000 km a year). Charging is 75% at home at €0.25/kWh, 15% on public AC at €0.45/kWh and 10% on DC fast chargers at €0.65/kWh.
- Home: 17 ÷ 0.90 × 0.25 = €4.72 per 100 km
- Public AC: 17 ÷ 0.90 × 0.45 = €8.50 per 100 km
- DC fast: 17 ÷ 0.95 × 0.65 = €11.63 per 100 km
Weighted by the 75/15/10 mix, the blended figure is €5.98 per 100 km, or about €0.06 per km (€0.096 per mile). Over 1,250 km that is €75 a month and about €900 a year, drawing roughly 235 kWh a month from the grid. A typical 20→80% top-up at home adds 36 kWh (≈ 212 km of range) for €10; a full 0→100% home charge costs €16.67, while the same full charge on a DC fast charger costs about €41.
The comparison petrol car uses 6.5 L/100 km at €1.75/L, i.e. €11.38 per 100 km and €142 a month. The EV saves around €810 a year, 47% less for energy. Put differently, petrol would have to fall to €0.92/L before it matched the EV’s running cost.
How to read the results
- Cost per 100 km is the headline number to compare cars and charging habits. Compare it with the petrol figure in the hint.
- Charge from/to reflects how people actually charge: most top up between 20% and 80%, which is also kinder to the battery.
- Petrol-equivalent price is the petrol price per litre at which both cars would cost the same per kilometre.
- CO₂ per year uses your grid factor and the grid energy including losses; solar-charged energy counts as zero. The petrol comparison is tailpipe only.
- The consumption table shows how sensitive costs are to driving style and season: winter consumption is commonly 15–30% higher.
Typical values
| Charging method | Typical price (Europe) | Typical loss | Cost per 100 km at 17 kWh |
|---|---|---|---|
| Home, off-peak EV tariff | €0.08–0.15/kWh | 8–12% | €1.50–2.80 |
| Home, standard tariff | €0.20–0.35/kWh | 8–12% | €3.80–6.60 |
| 2.3 kW domestic socket | same as home | 15–25% | 10–15% more than a wallbox |
| Public AC (11–22 kW) | €0.35–0.60/kWh | 8–12% | €6.60–11.30 |
| DC fast (50–350 kW) | €0.50–0.85/kWh | 3–7% (in car) | €9.00–15.20 |
| Petrol car, 6.5 L/100 km | €1.50–2.00/L | — | €9.75–13.00 |
Tips to cut your charging cost
- Charge at home whenever you can. Shifting even 20% of your charging from DC to home cuts the blended cost noticeably. Try it with the share sliders.
- Use an off-peak or dynamic EV tariff. Night rates of €0.08–0.15/kWh roughly halve home charging cost.
- Charge from your own solar. Midday charging from a home solar system is worth only the export price you forgo; a home battery can extend that into the evening.
- Avoid the granny cable for routine use. A 2.3 kW socket wastes far more energy than a 7–11 kW wallbox.
- On road trips, stop at 80%. The last 20% charges slowly (see the EV charging time calculator) and some networks bill by time.
- Check subscriptions. If you fast-charge more than a few times a month, a network subscription often pays for itself.
Limitations
Prices are taken as flat per-kWh figures. Some public chargers add session fees, time-based charges or idle fees, and some countries apply roaming surcharges; add an average to the subscription field if relevant. Consumption is a single annual average; very cold weather, motorway speeds and short trips with cabin preheating raise it. Battery degradation and pre-conditioning energy are not modelled separately. For the full ownership picture — purchase price, maintenance, insurance and resale — use the EV vs petrol car calculator.
Method & assumptions
Cost per 100 km for each method = consumption (kWh/100 km) ÷ (1 − charging loss) × price per kWh. Your blended cost weights the three methods by your charging shares. Monthly cost = blended cost per 100 km × km ÷ 100 + subscriptions. Solar-charged energy is valued at the export price you give up.
Frequently asked questions
How much does it cost to charge an electric car at home?
How much does it cost to charge an EV per 100 km?
Is fast charging more expensive than charging at home?
How much energy is lost when charging an EV?
Is an electric car cheaper to run than a petrol car?
How do I convert to cost per mile?
Sources & references
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