EV Charging Time Table – Battery Size & Charger Power

EV charging time from 20% to 80% on AC power

The 20–80% window adds 60% of the usable battery capacity. Choose the battery row and the effective power column. Times are shown as hours:minutes and are rounded to the nearest minute.

Example: a 60 kWh usable battery needs 36 kWh to move from 20% to 80%. At a constant battery-side 11 kW, the ideal time is 36 ÷ 11 = 3.27 hours, or about 3 hours 16 minutes.

How many kWh must be added for each charge window?

Charging time begins with the energy gap, not with the full battery label. A car charged from 40% to 80% adds only 40% of its usable capacity. This table gives the battery energy for four common windows.

The same percentage can represent very different energy. A 20–80% session adds 24 kWh to a 40 kWh battery but 60 kWh to a 100 kWh battery, before any charging losses are considered.

Ideal DC fast-charging time from 10% to 80%

This table uses average battery-side power maintained across the entire 10–80% window. It does not use the charger’s peak rating. That distinction is essential because a car may touch its peak only briefly and usually reduces power as state of charge rises.

A 70 kWh battery adds 49 kWh from 10% to 80%. If the session truly averages 100 kW into the battery, the energy-only time is about 29 minutes. A 100 kW peak does not guarantee that average.

The formula behind the charging time table

First calculate the change in state of charge as a decimal. Then multiply by usable capacity and divide the resulting energy by the effective average power.

For 20% to 80%, the state-of-charge difference is 0.80 − 0.20 = 0.60. The formula is dimensionally consistent: kWh divided by kW gives hours. Multiply decimal hours by 60 to obtain minutes.

Do not add the starting and ending percentages. A move from 20% to 80% is a 60-percentage-point increase, not a request for 100% of the battery.

Available power is the lowest limit in the charging chain

The number written on the charging station is only one ceiling. Actual power can also be restricted by the electrical connection, charging cable, vehicle inlet, onboard AC charger, battery-management system, temperature and state of charge.

On AC, the vehicle’s onboard charger converts grid AC to battery DC. A car with an 11 kW onboard charger cannot take 22 kW AC merely because the post offers it. It will normally be limited to its supported AC configuration, and single-phase or three-phase compatibility can matter.

On DC, conversion occurs in the charging equipment and power is supplied directly to the vehicle’s high-voltage system. The car still controls the acceptable current and voltage, so the station and vehicle must agree on a power level throughout the session.

Level 1, Level 2 and European AC power labels

Naming conventions vary by market. Power in kW, energy in kWh and the tested SOC window are more portable comparison data than the words “slow”, “fast” or “rapid”.

Peak power is not average charging power

A DC charging curve usually changes throughout the session. Power may be low when a cold battery first connects, rise after conditioning, remain on a plateau and then taper as the battery approaches a high state of charge. The advertised maximum is the highest point the system may reach under suitable conditions.

Average power across the chosen window is calculated from energy added divided by elapsed time. If a 77 kWh usable battery moves from 10% to 80%, it adds 53.9 kWh. Completing that window in 27 minutes implies an average battery-side power of approximately 120 kW, even if the vehicle briefly peaks much higher.

This is why the DC table must not be read by placing every vehicle under the column matching the charger sign. Use a documented session average or compare the manufacturer’s or tester’s time for the same SOC window.

Charging losses and wall-to-battery time

The tables start with energy entering the usable battery. A meter at home or a public charger measures energy supplied on the grid side, which also covers conversion, electronics, thermal management and other losses. If 36 kWh must reach the battery, the charger normally supplies more than 36 kWh.

Losses do not translate into one universal time surcharge. Some loads are relatively fixed, some depend on power, and battery heating or cooling can change during the session. A simple estimate can use measured average battery-side power; this automatically reflects the net rate at which battery energy was added.

For electricity cost, use grid energy rather than the ideal battery energy in this table. The EV Charging Cost Calculator separates those two quantities and lets you apply an explicit loss assumption.

Worked examples

Home charging a 77 kWh battery from 20% to 80%

The charge window is 60%, so the battery must gain 77 × 0.60 = 46.2 kWh. At an ideal constant 11 kW, time is 46.2 ÷ 11 = 4.20 hours, or 4 hours 12 minutes. If a measured session averages 9.8 kW into the battery, the same energy takes about 4 hours 43 minutes.

DC charging the same battery from 10% to 80%

The required battery energy is 77 × 0.70 = 53.9 kWh. At a true 120 kW average, time is 53.9 ÷ 120 × 60 = 27 minutes. A station rated at 150 kW does not establish a 150 kW average.

An overnight top-up, not a full recharge

An 80 kWh battery moving from 50% to 80% adds 24 kWh. Ideal time at 7.4 kW is 24 ÷ 7.4 = 3 hours 15 minutes. Using the full 80 kWh in the numerator would overstate the session.

Why the real charging time changes

• Battery temperature: a cold or very hot battery may accept less power until conditions improve.
• Starting and target SOC: the high-SOC portion often charges more slowly, particularly on DC.
• Vehicle limit: onboard AC capacity and the DC charging curve are model-specific.
• Shared equipment: some sites divide available power between connected vehicles.
• Battery conditioning: heating or cooling can consume power and affect the initial rate.
• Installation and supply: circuit current, voltage, phases and local load management may reduce AC power.
• Session overhead: connection, authentication, communication and balancing add time beyond the simple energy quotient.

Preconditioning may help a compatible vehicle reach a better DC charging curve, but the effect depends on the car and conditions. It should not be added as a fixed percentage to every estimate.

When to use this table

Use the table for a quick capacity-and-power comparison, an overnight parking check or a plausibility test for a quoted charge time. It is also useful for understanding why doubling available power approximately halves ideal time only while no other limit becomes active.

Use vehicle-specific charging data for route planning. A trip depends on arrival SOC, target SOC, charger availability, the actual DC curve, temperature and energy consumption on the road. The EV Range Calculator handles battery reserve and route distance; it does not replace live charger information.

Electrical equipment and circuits must be suitable for the intended continuous load. Follow the vehicle and charging-equipment instructions and use qualified installation where required.

Common errors when estimating EV charging time

Limits of the charging time table

• Every time is an ideal energy quotient rounded to the nearest minute.
• No fixed charging-loss percentage is built into the values.
• Battery size means usable capacity; gross nameplate capacity can be larger.
• AC and DC capability, voltage and phase support differ between vehicles.
• The table does not model a vehicle-specific DC charging curve.
• Temperature, battery health, conditioning, shared power and session overhead are excluded.
• Very short theoretical DC times may be physically unavailable to a given car.

Treat the numbers as transparent reference points. A reliable journey plan needs current vehicle, weather and charging-site data.