Solar Panel Count Calculator
Estimate how many solar panels you need for your energy usage and panel wattage free in your browser with this solar panel count calculator.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the daily energy needed, panel size and sun hours.
- Press Calculate.
How it works
Panels = daily energy needed (Wh) ÷ (panel watts × peak sun hours), rounded up.
Worked example
10 kWh/day, 400 W, 5 sun hours. = 5 panels.
Common mistakes
- Sizing from nameplate watts only — derate for sun-hours, losses and panel wattage to get a real count.
- Ignoring roof space and inverter limits, which can cap the array below the calculated count.
Frequently asked questions
How many solar panels do I need?
Divide your target daily kWh by the energy one panel makes (panel watts × sun-hours × ~0.78 ÷ 1000), then round up.
Do bigger panels mean fewer panels?
Yes — higher-wattage panels reach the same system size with fewer units, which helps when roof space is tight.
Should I add extra panels for losses?
Yes — real systems lose roughly 10–25% to wiring, heat, dirt and inverter inefficiency, so size up rather than aiming for the bare minimum.
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Cite this tool
Zerdly. (2026). Solar Panel Count Calculator. Retrieved from https://www.zerdly.com/tools/solar-panel-count-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.