What does your EV charging result mean?
The calculator separates energy used by the vehicle from electricity drawn from the grid. It then prices the home and public charging shares separately so you can see what driving distance, charging losses and charging location do to the monthly cost.
Change an input above and this interpretation updates automatically.
Continue your calculation
EV charging is one part of the household energy picture. These tools let you continue with the same numbers instead of starting from an unrelated estimate.
How does the EV charging cost calculator work?
First, the calculator estimates the energy the vehicle needs for the entered driving distance. If the car uses 18 kWh/100 km and you drive 1,200 km per month, the battery-energy estimate is 216 kWh per month.
Charging is not perfectly loss-free. If the entered loss is 10%, the calculator treats the charging process as 90% efficient and increases the required grid energy accordingly.
The grid energy is then divided between home and public charging. Each part is multiplied by its own price per kWh and the two costs are added together.
Battery energy vs grid energy
Battery energy is the driving-energy estimate based on kWh/100 km. Grid energy is the electricity that must be supplied by the charger after the loss assumption is included.
The difference is shown as charging losses. This distinction matters when you estimate cost from an in-car consumption figure but pay for electricity measured at the socket or charging station.
When should charging losses be set to 0%?
If your consumption figure already represents electricity measured at the wall or charger for the same driving distance, adding a separate charging-loss percentage can count the losses twice.
In that case, use 0% losses or convert the source value back to a battery-side figure before using an additional loss assumption. Always check how the source defines its kWh/100 km number.
Where should you get the input data?
| Input | Useful source | What to check |
|---|---|---|
| Driving distance | Odometer, trip log, navigation history or monthly travel estimate | Use the same period you want to budget for. |
| Vehicle consumption | Trip computer, charging app, long-term vehicle average or official efficiency information | Check whether it is battery-side or already includes grid charging losses. |
| Charging losses | Measured charger/grid energy compared with vehicle energy, or a documented assumption | Losses vary with charger, power level, temperature and charging conditions. |
| Home charging share | Charging history or a realistic monthly estimate | Enter a percentage from 0% to 100%. |
| Home price | Electricity tariff or bill | Use the marginal price relevant to EV charging, especially with time-of-use tariffs. |
| Public price | Charging-network app, tariff or station price | Check whether session, parking, subscription or idle fees apply separately. |
Good to know: charging losses are real, but not one fixed percentage
Charging equipment and the vehicle use some energy before it reaches the traction battery. The loss can change with AC or DC charging, power level, temperature, battery conditioning and other vehicle-specific behaviour. Treat the percentage as a scenario input, not a universal constant.
What affects EV charging cost the most?
The largest drivers are usually straightforward. Driving more kilometres increases energy use almost proportionally. A higher kWh/100 km value increases the battery energy required for the same distance. Charging losses increase the grid kWh you pay for, while the home/public split determines which electricity price is applied to those kWh.
| Change | Expected effect |
|---|---|
| Distance +10% | Battery energy, grid energy and charging cost rise by about 10% if the other inputs stay unchanged. |
| Consumption +10% | Energy and cost rise by about 10% for the same driving distance. |
| Higher charging losses | Grid energy rises even though the driving-energy requirement is unchanged. |
| More charging at the cheaper location | The blended electricity price falls if that location really has the lower marginal price. |
Does your EV charging result look realistic?
Start with the units. The vehicle input is kWh per 100 km, not kW, litres/100 km or the usable battery capacity in kWh. Then check whether the monthly distance is realistic and whether the public and home prices are prices per kWh rather than a complete monthly bill.
If grid energy is unexpectedly high, check the charging-loss percentage. A value entered as 10 means 10%, not 0.10%. If charging cost is unexpectedly high, verify that a public price such as 0.60 is actually 0.60 currency units per kWh and not 60 cents entered as 60.
A result can also look wrong when the consumption source already includes charging losses. In that situation, the separate loss input can double-count them.
Worked example: 1,200 km per month with mixed charging
Assume an EV travels 1,200 km per month and averages 18 kWh/100 km. Battery energy for driving is therefore:
With 10% charging losses, grid energy becomes:
If 80% is charged at home for €0.30/kWh and 20% publicly for €0.55/kWh, home charging uses 192 kWh and public charging 48 kWh. The cost is:
That equals €1,008 per year if the same monthly scenario repeats, or €7.00 per 100 km. The 10% loss assumption adds 24 kWh of grid energy per month above the 216 kWh estimated for driving.
How much can the charging location matter?
With the worked-example prices, the public price is €0.25/kWh higher than the home price. The current public share is 48 kWh per month, so those public kWh add €12 per month compared with charging the same energy at home.
This does not mean home charging is always cheaper. Compare the actual marginal home tariff, public tariff and any extra fees that apply to your situation.
Home time-of-use tariffs
A single home price is an average scenario. If your tariff has cheap off-peak hours and expensive peak hours, use the price that best represents when the EV actually charges.
For a more detailed comparison, calculate separate scenarios for off-peak and peak charging rather than hiding a very wide tariff difference inside one average value.
Practical tip
When comparing charging strategies, change one variable at a time. Keep distance, vehicle consumption and charging-loss assumption unchanged, then compare the home/public split or prices. That makes the cost difference easy to explain.
kW, kWh and kWh/100 km are different
kW is power — for example, the charging rate of a charger. kWh is energy — for example, 40 kWh delivered during a charging session. kWh/100 km is vehicle energy consumption over distance.
This calculator estimates energy and cost, not charging time. A 7 kW wallbox does not mean the car uses 7 kWh/100 km. Charging time also depends on battery state of charge, the vehicle's onboard charger, charging curve and available electrical power.
What is not included in the result?
The result prices electricity only. It does not automatically include public-charging subscriptions, session fees, parking fees, idle fees, charger installation, wallbox finance, battery degradation, road charges or the purchase price of the vehicle.
It also assumes the same monthly driving pattern repeats for the annual figure. Seasonal consumption can change because cabin heating, air conditioning, battery conditioning, tyres, speed and weather can all change the energy required per 100 km.
If a public network uses a tariff that is not based only on kWh, treat the calculator as the electricity component of the charging cost and add the separate fee outside the model.
What should you do with the result?
Use the monthly and per-100-km figures as a repeatable baseline. If you are deciding whether a home charger or a different tariff is worthwhile, keep the same distance and vehicle consumption and change only the charging mix or electricity price.
If you have solar PV, compare how much EV charging can realistically be shifted into solar-production hours rather than assuming every EV kWh is free. If you want to understand the wider household bill, move the estimated grid kWh into the Electricity Cost Calculator.
For budgeting, update the calculation when your real long-term consumption, driving distance or charging pattern changes. A measured multi-month average is usually more useful than one unusually efficient or inefficient trip.
For automotive and electrical-technology students
This calculator is useful for learning the difference between vehicle energy consumption and the electricity that must be supplied by the grid. The core idea is energy balance: the car needs a certain amount of battery energy for a distance, while the charger must supply more when losses occur.
Exercise: An EV travels 500 km per month at 16 kWh/100 km. Charging losses are 12%. Of the grid energy, 75% is charged at home for €0.28/kWh and 25% publicly for €0.60/kWh. Calculate battery energy, grid energy, monthly cost and cost per 100 km.