To keep a solar generator topped up, your panels need to put back the energy you use each day. The calculator estimates the panel wattage needed from your daily use, the peak sun hours where you are, and a real-world efficiency factor.
Peak sun hours vary by location and season; use a conservative figure for winter.
- Panel wattage needed
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- Note
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The formula
Panel watts needed = energy to replace (Wh) ÷ (peak sun hours × real-world efficiency).
Example: replacing 800 Wh with 4 peak sun hours at 75% efficiency needs about 800 ÷ (4 × 0.75) ≈ 267 W of panels.
About the inputs
- Peak sun hours are the equivalent number of hours of full-strength sunlight per day. They vary by location, season and weather; winter values are much lower than summer values in most of the US. Use a conservative number if you depend on solar.
- Real-world efficiency covers losses from panel angle, heat, dust, partial shade, wiring and the charge controller. Portable panels laid flat on the ground often produce well below their rated wattage.
- Solar input limit: every power station has a maximum solar input in watts, plus voltage and current limits. Extra panel wattage beyond that limit is wasted, and exceeding the voltage limit can damage the unit. Check the manual.
For connecting more than one panel, read series vs parallel solar panels. For charging time estimates, see how long a solar generator takes to charge.
