Solar Charging Time Calculator
Estimate how many hours of sun it will take to recharge your battery or power station with a given solar panel, under different sun conditions.
Estimated Charging Time
Estimated charging time
5.3 hours
under average sun
Equivalent good-sun hours
4.5 hours
A 200W panel does not produce exactly 200W continuously — real output rises and falls through the day and varies with weather, so this is a planning estimate, not a guaranteed charge time. Charging also typically slows as a battery approaches 100%, which this estimate does not model in detail.
Formula
Charging hours = (energy needed) ÷ (panel wattage × system efficiency), where energy needed = (target % − starting %) × battery capacity. We apply a lower efficiency assumption for poorer sun conditions to reflect real-world losses from cloud cover, angle and temperature.
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Frequently Asked Questions
Why doesn't my panel charge as fast as its rated wattage suggests?+
Rated wattage is measured under ideal, standardised lab conditions. Real-world charging is affected by cloud cover, panel angle relative to the sun, shading, dust, temperature, and time of day — actual output is often well below the rated figure for meaningful portions of the day.
Does charging slow down near 100%?+
Yes, many battery management systems taper charging current as the battery approaches full to protect the cells — this calculator gives a straight-line estimate and doesn't model that tapering in detail, so treat the final stretch to 100% as potentially slower than shown.
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