Time-of-Use EV Charging Calculator
Estimate monthly charging cost and potential savings from moving electric-car charging to a cheaper tariff period.
Currency selection changes the unit label, not an exchange rate. Enter every price in the selected currency.
How to choose the inputs
Enter energy purchased from the grid, including charging losses. This calculator moves that same energy between two tariffs; it does not add another efficiency adjustment. The shifted percentage is the share of kWh, not simply the share of charging sessions.
Formula and measurement boundary
Three worked scenarios
These are fixed hypothetical examples, not live tariffs or verified product data. They use EUR and kilometres where applicable and do not change with the form settings. Only the table input changes.
Unchanged inputs
- Monthly charging energy from grid: 300 kWh
- Day electricity price: 0.25 EUR/kWh
- Off-peak electricity price: 0.15 EUR/kWh
| Charging moved off-peak | Estimated result |
|---|---|
| 0 % | €0.00 month saved |
| 50 % | €15.00 month saved |
| 100 % | €30.00 month saved |
The all-day baseline is €75/month. Moving 0%, 50% or 100% gives scheduled bills of €75, €60 and €45. A zero shift means zero savings. The twelve-month projection repeats the same month.
What this result does not establish
- Fixed tariff-plan fees, demand charges and time-varying spot prices are not included.
- Available overnight hours and charger power are not checked.
- If the supposed off-peak price is higher, shifting increases costs; the annual saving becomes negative.
Check whether the cheap window can deliver the promised energy
The following are additional hypothetical decision examples. Separately discussed fees, reserve allowances or running costs are not automatically added to the form result.
An illustrative 60 kWh pack charged from 20% to 80% needs 36 kWh stored or 40 kWh from the supply at 90% efficiency. A four-hour cheap window with 7 kW input can supply only 28 kWh. The other 12 kWh must be delivered outside the window, unless the session starts earlier, ends later or requires less energy. A tariff-share assumption alone cannot verify the schedule.
At €0.12/kWh in the cheap period and €0.30/kWh outside it, 28 cheap kWh plus 12 expensive kWh costs €6.96. All 40 kWh at the expensive rate would cost €12.00; the session saving is €5.04. If moving to the tariff adds €6/month fixed cost, one such session per month is insufficient to recover that additional fee. Compare annual frequency and the whole-house bill.
Weight prices by input kWh and use the contract’s actual clock periods, including any seasonal or weekend distinctions. If smart charging pauses because other household loads consume the available power, the achievable cheap-energy share can fall. Confirm the departure percentage after several real scheduled sessions before relying on an assumed share every night.
Sources and their scope
- EIA: measuring electricity — Power and energy units only; not equipment performance.
These reference pages were accessed on 21 September 2026. The equations and examples are the site’s own model; these sources do not certify its defaults or results.
Frequently asked questions
Does choosing a currency convert my tariff?
No. Currency changes the display label only. Enter all prices in the chosen currency.
Can the whole monthly energy move off-peak?
Only if your schedule, charger and tariff window allow it; the percentage is an assumption you provide.
Read the model and verification limits