How Long Does It Take to Charge an Electric Car? AC and DC Worked Examples

Start with the energy gap, not the size of the whole pack

A 60 kWh usable battery going from 20% to 80% needs 36 kWh stored in the battery: 60 × (80 − 20) ÷ 100. Dividing the full 60 kWh by a charger rating answers a different question. Check that the capacity is usable rather than gross and that it represents the scenario you intend to model.

Charging also uses energy that does not remain stored. With losses assumed to be 10% of grid energy, supplying 36 kWh requires 40 kWh from the grid. At a constant 7.4 kW, time is 40 ÷ 7.4 = 5.405 hours, which our calculator rounds upward to 5 hours 25 minutes. The 10% loss is an illustrative input, not a universal efficiency claim.

For AC, find the lowest compatible limit

An AC station supplies electricity to the car’s onboard charger. The effective rate depends on the station, installation and car together. A station marked 22 kW will not make an 11 kW car charge at 22 kW. A single-phase installation can also give a different result from the three-phase figure in a brochure.

The table holds energy and loss assumptions constant so that only available power changes. Treat the times as planning arithmetic. Supply restrictions, cabin heating and interruptions can alter a real session. For domestic-socket charging, use only equipment and an installation approved for that use by the manufacturer and a qualified electrician.

Will the session fit a four-hour cheap-rate window?

At 7.4 kW, four uninterrupted hours draw 29.6 kWh and store 26.64 kWh under the same 10% loss assumption. In a 60 kWh battery starting at 20%, that reaches 64.4%, short of the 80% target. A further 9.36 kWh must be stored, requiring approximately 1 hour 25 minutes at the same rate.

Enter 4 in the calculator’s optional AC charging-window field to see the end-of-window charge and remaining energy. A 20–80% charge is not necessarily required every night: if a normal day uses 12 kWh, replacing that energy needs about 1 hour 49 minutes at this rate. Base the schedule on your next journey and the car’s instructions, then check the tariff’s actual hours and any household power limit.

Why dividing by the DC peak is too optimistic

A peak DC rating describes a limit, not a promise that the battery accepts that power continuously. Starting charge, battery temperature and the charging curve affect the average. Preconditioning, where supported, may help prepare the battery, but follow the vehicle’s instructions rather than assuming every model has the same feature.

For a transparent illustration, choose a 150 kW station and vehicle limit, a 60% average-power factor below 80%, and 10% losses. The effective stored-energy rate below 80% is 150 × 0.60 × 0.90 = 81 kW. Adding 36 kWh from 20% to 80% therefore takes about 27 minutes in this model. Dividing by the 150 kW peak alone would give 14.4 minutes and ignore both assumptions.

The chosen 60% factor is not a measured charging curve for a particular car. If you have a manufacturer charging-time specification, retain its starting charge, temperature, station requirements and test conditions when comparing it.

Why the last 20% can take a disproportionate amount of time

Above 80%, this calculator halves the selected average-power factor. In the same fictional DC scenario, 80–100% adds only 12 kWh but takes about 18 minutes. The whole 20–100% session takes about 45 minutes, rather than 27 minutes to 80%. These are separately rounded outputs from a deliberately simple two-part curve.

The result can help compare a shorter stop with a longer charge, but it cannot choose the correct stop for your route. The next reliable charger, arrival reserve and weather may justify charging beyond 80%. Include detours, queues and payment or connection time in your travel schedule; none of those is included in battery charging time.

Record one session so the next estimate is better

Keep the starting and ending charge, elapsed charging time, charger energy, outside conditions and any power limit displayed by the car. Separate time connected from time actually charging. These observations can help select a more realistic average-power assumption, but a single unusual session should not be used to diagnose battery degradation.

If power is unexpectedly low, compare the station and vehicle limits, starting charge and temperature before blaming capacity loss. Record warning messages and ask the charging operator or a qualified vehicle technician to investigate persistent problems. The practical value of the calculator is showing which assumption changes the timetable, with the calculation visible beside it.