EV Charging Time Calculator

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Electric vehicle charging time describes the span needed for a pack to climb from one state of charge to another once you select a specific power supply.

Reliable scheduling depends on knowing that span because road trips, depots, and residential load management all expect a confident finish window.

This tool lets you enter pack capacity, arrival charge, goal charge, and charger characteristics, then folds in efficiency losses, climate penalties, and idle minutes so the estimate mirrors a real session.

Advanced controls stay optional, so you start with headline values and layer taper or pricing when you have the measurements.

For instance, a 75 kWh battery that arrives at 20% and targets 80% on a 7.2 kW charger with 92% efficiency completes in roughly 6.25 hours while drawing about 48.8 kWh from the grid.

Technical Details:

The core quantity is the battery energy required to shift from the starting state of charge to the target. Multiplying pack capacity by the SOC delta yields kilowatt-hours that must actually land in the cells.

The charger contributes a baseline power level that may be shaved by climate or load penalties. Active charging time divides each stage’s energy by the effective power and keeps tapering separate so a high-power stall that throttles near full can be modelled faithfully.

Efficiency losses expand the wall draw beyond battery energy, while idle or preparation minutes add both time and consumption at the untapered power level. Session cost attaches by multiplying grid energy by the chosen tariff.

\begin{matrix} E_{batt} & = & C pack \cdot \frac{{SOC}_{target} - {SOC}_{start}}{100} \\ P_{eff} & = & P_{charger} \cdot (1 - p_{penalty}) \\ t_{stage1} & = & \frac{E_{stage1}}{P_{eff}} \\ t_{stage2} & = & \frac{E_{stage2}}{P_{eff}} \\ t_{total} & = & t_{stage1} + t_{stage2} + t_{idle} \\ E_{grid} & = & \frac{E_{batt}}{η_{charger}} + P_{eff} \cdot t_{idle} \end{matrix}

Symbols & Units

Symbol	Meaning	Unit / Type	Source
Cpack	Battery capacity	kWh	User input
SOCstart	Arrival state of charge	percent	User input
SOCtarget	Target state of charge	percent	User input
Pcharger	Rated charger power	kW	User input
ppenalty	Climate or load penalty	fraction	User input
ηcharger	Charging efficiency	fraction	User input
rtaper	Power fraction after taper	fraction	User input
tidle	Idle or setup duration	hours	User input
Ebatt	Energy delivered to the pack	kWh	Computed
Egrid	Total grid energy	kWh	Computed

Worked example

\begin{matrix} E_{batt} & = & 75 \cdot \frac{80 - 20}{100} = 45 kWh \\ P_{eff} & = & 7.2 \cdot (1 - 0.10) = 6.48 kW \\ t_{active} & = & \frac{45}{6.48} = 6.94 h \\ E_{grid} & = & \frac{45}{0.92} + 6.48 \cdot 0.17 = 48.8 kWh \end{matrix}

Interpretation: charging the example vehicle takes about 6 hours and 56 minutes including ten idle minutes and consumes 48.8 kWh from the supply.

Rounding and precision

Durations are rounded to the nearest minute for display, while internal math keeps double precision.
Energy values show two decimal places using the locale decimal separator.
Cost reporting multiplies unrounded energy by the tariff before rounding to two decimals.

Validation and bounds

Field	Type	Min	Max	Step / Pattern
Battery capacity	Number	0	1,000	0.1
Current SOC	Number	0	100	1
Target SOC	Number	0	100	1
Charger power	Number	0	500	0.1
Charging efficiency	Number	50	100	0.1
Climate penalty	Number	0	90	1
Taper begins at	Number	0	100	1
Taper power	Number	5	100	1
Idle & setup time	Number	0	180	1
Electricity price	Number	0	10	0.001
Currency code	Text	3 chars	6 chars	Uppercase letters

Privacy & compliance

All calculations run in your browser, and no charging inputs leave the page.

Performance note

The timeline chart renders a handful of breakpoints, so even large adjustments stay responsive on typical laptops and tablets.

How-to:

1Enter the pack capacity in kilowatt-hours from the vehicle specification sheet.
2Set current and target states of charge to match your arrival and departure plan.
3Pick a preset or input the charger power your site delivers.
4Open Advanced to represent taper, climate derate, idle minutes, or tariffs when needed.
5Review the breakdown, copy CSV or JSON for planning sheets, and watch the chart for taper impact.

Example: Enter 82 kWh, 25% arrival, 90% target, 11.5 kW charger, 95% efficiency, 5% penalty for a cold night, taper at 85% with 50% power, and 15 idle minutes.

The tool returns about 5 hours 40 minutes total, 55.3 kWh grid draw, and a clear view of when taper slows the session.

Outcome: you leave with an exportable plan that matches real charging behaviour and cost expectations.

FAQ:

How long to charge a 75 kWh EV on a 7 kW charger?

Set 75 kWh, 10% arrival, 90% target, and 7 kW power. Expect roughly 8.6 hours without taper, or longer if you enable taper from 80%.

How precise is the taper model?

It applies a two-stage approximation that mirrors the plateau many fast chargers apply. For curved profiles you can lower the taper fraction or shorten the taper start to mimic vendor data.

What limits should I respect?

Keep SOC within 0 to 100, hold taper power above 5%, and ensure climate penalties stay below 90% so the charger can still move energy.

How are costs calculated?

Grid energy combines battery energy divided by efficiency and the idle draw, then multiplies by your tariff. Demand charges or time-of-use surprises must be added manually.

Does any data leave my device?

No. Inputs remain in the browser and exports are generated locally as CSV or JSON files.

Can I use this offline?

Yes. After the page loads once, the calculator continues to operate without a network connection because the computation is client-side.

Is there a cost to use the tool?

The calculator is provided without usage fees. Electricity cost estimates reflect your tariff entries only.