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EV Charging Time Calculator
Estimates how long an electric vehicle takes to charge between two states of charge from its battery capacity, the charger power (capped by the onboard charger for AC charging) and the charging efficiency, plus the energy drawn from the grid and its cost.
When to use
You want to know how long an EV needs on a home wallbox, a public AC post or a DC fast charger to reach a target charge, or what the session costs at a given electricity price.
Do not use when: You need a battery's charge time from ampere-hours and charger current (use battery-charge-time) or the driving range the added energy gives (use ev-range-efficiency); DC fast charging above about 80 % tapers strongly and takes longer than this constant-power estimate.
Formula
energy_added_kwh = battery_capacity_kwh × (target_percent − start_percent) / 100; energy_from_grid_kwh = energy_added_kwh / (charging_efficiency_percent / 100); effective_power_kw = min(charger_power_kw, max_onboard_charger_kw); charging_time_hours = energy_from_grid_kwh / effective_power_kw; cost = energy_from_grid_kwh × electricity_price_per_kwh
Constant-power model. AC charging is limited by the car's onboard charger (U.S. DOE: Level 1 ≈ 1.4 kW, Level 2 up to 19.2 kW); DC fast charging is limited by the car's charge curve and slows sharply above about 80 %, so real DC sessions to 100 % take considerably longer.
Inputs
| Parameter | Type | Unit | Required | Description |
|---|---|---|---|---|
battery_capacity_kwh | number | kWh | yes | Usable battery capacity in kilowatt-hours (e.g. 40, 60, 75, 100). Range: > 0, ≤ 1000 |
start_percent | number | % | default 20 | State of charge at the start of the session. Range: ≥ 0, ≤ 100 |
target_percent | number | % | default 80 | State of charge to reach; must be higher than start_percent. Range: ≥ 0, ≤ 100 |
charger_power_kw | number | kW | yes | Power the charging point delivers: 1.4–2.3 kW household socket (Level 1), 7–22 kW wallbox / AC post (Level 2), 50–350 kW DC fast charger. Range: > 0, ≤ 1000 |
max_onboard_charger_kw | number | kW | no | Optional maximum AC charging power of the car's onboard charger (commonly 7.4 or 11 kW); the effective power is the lower of the two. Omit for DC charging. Range: > 0, ≤ 1000 |
charging_efficiency_percent | number | % | default 90 | Share of grid energy stored in the battery; 85–92 % is typical for AC charging (onboard charger and battery losses). Range: ≥ 50, ≤ 100 |
electricity_price_per_kwh | number | per kWh | no | Optional price per kWh in your currency for the cost of the session (grid energy × price). Range: ≥ 0, ≤ 100 |
Outputs
| Output | Type | Unit | Description |
|---|---|---|---|
energy_added_kwh | number | kWh | battery_capacity_kwh × (target_percent − start_percent) / 100. |
energy_from_grid_kwh | number | kWh | energy_added_kwh / efficiency (what the meter records). |
effective_power_kw | number | kW | min(charger_power_kw, max_onboard_charger_kw). |
charging_time_hours | number | h | energy_from_grid_kwh / effective_power_kw. |
charging_time_text | string | Charging time as hours and minutes, e.g. "7 h 9 min". | |
cost | number | energy_from_grid_kwh × electricity_price_per_kwh; only when a price is given. | |
range_note | string | Approximate driving range the added energy gives at an example consumption of 160 Wh/km. |
Example
75 kWh, 20 → 80 %, 7 kW wallbox, 90 %, 0.30 per kWh: {"battery_capacity_kwh":75,"start_percent":20,"target_percent":80,"charger_power_kw":7,"charging_efficiency_percent":90,"electricity_price_per_kwh":0.3} → {"energy_added_kwh":45,"energy_from_grid_kwh":50,"effective_power_kw":7,"charging_time_hours":7.14,"charging_time_text":"7 h 9 min","cost":15}
60 kWh, 10 → 100 %, 11 kW post, 7.4 kW onboard charger: {"battery_capacity_kwh":60,"start_percent":10,"target_percent":100,"charger_power_kw":11,"max_onboard_charger_kw":7.4} → {"energy_added_kwh":54,"energy_from_grid_kwh":60,"effective_power_kw":7.4,"charging_time_hours":8.11,"charging_time_text":"8 h 6 min"}
GET https://tttkmbb.com/api/v1/calculate/ev-charging-time?battery_capacity_kwh=75&start_percent=20&target_percent=80&charger_power_kw=7&charging_efficiency_percent=90&electricity_price_per_kwh=0.3
Machine access
- API:
GET https://tttkmbb.com/api/v1/calculate/ev-charging-time(query parameters) orPOSTwith a JSON body{"inputs": {...}} - Schema: https://tttkmbb.com/api/v1/calculators/ev-charging-time · Markdown: https://tttkmbb.com/energy/ev-charging-time.md · JSON definition: https://tttkmbb.com/energy/ev-charging-time.json
- MCP: server
https://tttkmbb.com/mcp, toolestimate_ev_charging_time - OpenAPI operationId:
estimate_ev_charging_time - Freshness:
static. Authentication: none. Rate limit: fair use (see rate limits).
Sources
FAQ
Why is my car charging slower than the wallbox rating?
The onboard charger caps AC power (many cars accept 7.4 kW single-phase or 11 kW three-phase), and cold or nearly full batteries reduce the rate further. Enter the onboard limit in max_onboard_charger_kw.
Does the efficiency change the cost?
Yes. The meter records grid energy, which is the battery energy divided by the efficiency, so a 90 % efficient session costs about 11 % more than the energy stored.
How long does DC fast charging take?
The estimate holds for 10–80 %; above 80 % chargers taper to protect the battery, and the last 20 % can take as long as the first 70 %.
Related calculators
- EV Range and Efficiency Calculator — Range the added energy gives at the car's consumption.
- Battery Charge Time Calculator — Charge time from ampere-hours and charger current.
- Electricity Cost Calculator — Cost of the same kWh at several tariffs.