Minimum charging window calculator

With constant charging power and adequate capacity, account for both charging and later discharge losses when sizing the charging window; standby losses are excluded.

t_{\text{ch}} = \frac{E_{\text{ac}} \times 100 \times 100}{P_{\text{ch}} \times \eta_{\text{ch}} \times \eta_{d}}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Worked example

Given

$E_{\text{ac}}$ = 300 kWh
$P_{\text{ch}}$ = 100 kW
$\eta_{\text{ch}}$ = 88 %
$\eta_{d}$ = 93 %

t_{\text{ch}} = \frac{300 \times 100 \times 100}{100 \times 88 \times 93} \approx 3.666

Symbols and units

Symbol	Meaning	Unit
$t_{\text{ch}}$	minimum charging time	h
$E_{\text{ac}}$	required later AC output	kWh
$P_{\text{ch}}$	constant AC charging power	kW
$\eta_{\text{ch}}$	charging efficiency	%
$\eta_{d}$	discharging efficiency	%

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Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.