Home EV Charger Size Calculator
Estimate available charging power and time from supply type, current limit, voltage and vehicle AC charging limit.
Currency selection changes the unit label, not an exchange rate. Enter every price in the selected currency.
How to choose the inputs
The vehicle limit must apply to the selected number of phases and available current. A headline three-phase AC rating cannot be assumed on a single-phase supply. Enter only current available after other household loads and any wallbox or cable limit; the tool has no separate wallbox input.
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
- Supply type: Three-phase
- Voltage: 400 V
- Available current: 16 A
- Usable battery capacity: 60 kWh
- Charge to add: 60 %
| Vehicle AC limit | Estimated result |
|---|---|
| 3.6 kW | 3.6 kW available |
| 7.2 kW | 7.2 kW available |
| 11 kW | 11 kW available |
The balanced supply estimate is 11.09 kW. The table then applies three assumed compatible vehicle limits. These are arithmetic scenarios, not proof that a particular car can accept those powers on this supply.
What this result does not establish
- Phase compatibility and the on-board charger topology are not checked.
- The time estimate assumes a fixed 90% charging efficiency and constant power.
- Cable sizing, protection, earthing and load management require a qualified installer.
Size for the daily refill window, not for an empty battery
The following are additional hypothetical decision examples. Separately discussed fees, reserve allowances or running costs are not automatically added to the form result.
A hypothetical driver covering 60 km/day at 20 kWh/100 km needs to replace 12 kWh at the battery. At 90% charging efficiency this requires 13.33 kWh from the supply. An eight-hour charging window needs only 1.67 kW average input. A 150 km day at 24 kWh/100 km needs 40 kWh from the supply and 5 kW over the same window. These two scenarios show why the usual commute and an occasional long day deserve separate checks.
A 22 kW wallbox cannot force a vehicle to accept 22 kW. The effective ceiling is the lowest relevant limit: vehicle AC acceptance, wallbox setting, available supply and load-management allowance. Phase configuration also matters. Do not assume the whole nominal house connection remains available when heating, cooking and other loads run.
Use the result as an energy-window requirement, then ask an installer to verify phases, protection, circuit capacity and dynamic load balancing. Check that the tariff’s cheap window is as long as the charging window entered. Buying more rated power does not lower the number of kWh needed for the same journey; it only changes the possible delivery rate.
Sources and their scope
- Schneider Electric: apparent power — Single-phase and balanced three-phase relationships.
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 a 22 kW wallbox make any car charge at 22 kW?
No. Supply, wallbox, cable and phase-specific vehicle limits all have to support that power.
Does the result approve my installation?
No. It is an upper-bound arithmetic comparison, not an installation assessment.
Read the model and verification limits