EV Charging Time Calculator
Charging time and grid energy from battery size, state of charge range and charger power. With the formula, a worked example and typical values.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
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About this calculator
This page calculates energy into battery, energy from grid and charging time from battery capacity, start charge, target charge, charger power and 1 more input. Change any value or its unit and the result updates. The steps below show the working for the default values, so you can check each line against your own method.
Limits of this calculator
Charging slows above about 80%, so real times to 100% are longer than this linear estimate.
Cross-check: 6 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Indicative
Indicative. Estimation only; further engineering checks are required. Basis: Constant-power charging estimate.
What this calculator checks
- The arithmetic of the simplified model for the values you entered.
What remains unverified
- Whether the simplifying assumptions listed on this page hold for your case.
- Any standard, manufacturer or site data. Treat the result as an estimate and confirm it by a further engineering check.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | Not applicable: Energy divided by charging power is a general estimate. EV charging standards specify EVSE characteristics, connection and safety, not a universal charging-time equation for all vehicles and charge profiles. |
| Standard review state | Not applicable |
| Scope-screening note | not recorded |
| Cross-check test cases | 6 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Indicative |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Battery capacity | 60 kWh |
| Start charge (%) | 20 |
| Target charge (%) | 80 |
| Charger power (AC supply) | 11 kW |
| Charging efficiency | 0.9 |
- Eb = 60 × 60 % = 36 kWh
- Eg = 36 / 0.9 = 40 kWh
- t = 40 / 11 = 3.636 h
Assumptions
- Constant charging power
- Vehicle onboard charger is not the limit
Charging slows above about 80%, so real times to 100% are longer than this linear estimate.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Battery capacity | kWh | greater than 0 kWh | |
| Start charge (%) | (number) | 0 or more, up to 100 | |
| Target charge (%) | (number) | 0 or more, up to 100 | |
| Charger power (AC supply) | kW | greater than 0 kW | |
| Charging efficiency | (number) | greater than 0, up to 1 |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Energy into battery | kWh | Shown to 1 decimal place | |
| Energy from grid | kWh | Shown to 1 decimal place | |
| Charging time | h | Shown to 2 decimal places |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
How the result changes with battery capacity
| Battery capacity (kWh) | Energy into battery (kWh) | Energy from grid (kWh) | Charging time (h) |
|---|---|---|---|
| 6 | 3.6 | 4 | 0.36 |
| 15 | 9 | 10 | 0.91 |
| 30 | 18 | 20 | 1.82 |
| 60 | 36 | 40 | 3.64 |
| 120 | 72 | 80 | 7.27 |
| 240 | 144 | 160 | 14.55 |
| 600 | 360 | 400 | 36.36 |
Other inputs are the same as in the worked example above.
Standards and further reading
- IEC 62548 (photovoltaic array design requirements)
Module and battery limits come from the manufacturer data sheet; local grid codes set connection rules. These are named as background reading. Elecmetric does not embed clause text or rating tables, and the reviewer record for this calculator is separate from this list.
Frequently asked questions
What do I need to enter?
Enter battery capacity, start charge (%), target charge (%), charger power (AC supply) and charging efficiency. Change the unit of a value with its selector and the result stays the same.
What does this calculator assume?
Constant charging power. Vehicle onboard charger is not the limit.
Which calculators should I use next?
Common next steps are Current from Power (kW to Amps) and Appliance Running Cost (Energy and Cost). The related links at the bottom of this page open them.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 6 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- EV Charging Time Formulas: Electric vehicle charging formulas: the power of a single-phase or three-phase charge point
- Battery Charge Time Formulas: Battery charge time formulas: ampere-hours to replace, charge efficiency, charge time from the charger current
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