Off-Grid Solar Calculators

Appliance-specific

Electric Bike / Onewheel Solar Charging Sizer

A 500 Wh e-bike pack needs more than 500 Wh from solar because the charger and inverter waste energy. Divide pack watt-hours by charger efficiency, then by peak sun hours and array derate.

Inputs

Units
Wh
h

Terms of Service

Results

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Engineering methodology

Energy drawn from solar = pack watt-hours ÷ charger (and inverter) efficiency. Array watts for one recharge in the entered sun window = that energy ÷ (peak sun hours × array derate). Direct DC MPPT e-bike chargers can skip the inverter; use a higher efficiency in that case.

Frequently asked questions

How much solar do I need to recharge a 500 Wh e-bike battery?

At 85% charger efficiency you need about 588 Wh from the array. With 5 peak sun hours and a 0.75 derate, array size ≈ 588 / (5 × 0.75) ≈ 157 W of nameplate panel for one full charge in that window.

Why isn’t array size just pack Wh divided by peak sun hours?

Charger and inverter waste energy, and panels do not deliver STC watts all day. Divide by efficiency, then by PSH × derate.

Can I charge an e-bike battery faster by oversizing the array?

The bike charger and BMS cap current. Extra panel watts beyond what the charger will accept do not shorten charge time. Do not exceed the charger’s input rating.

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