How to Calculate Solar Panel Sizing
What is Solar Panel Sizing?
Solar Panel Sizing Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Panels = Daily kWh / (Panel Watts × Peak Sun Hours × 0.80)
Step-by-Step Guide
- 1Calculate daily usage, divide by panel output accounting for efficiency
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
30 kWh/day, 300W panel, 5 peak sun hours
Result
Panels = 30/(300×5×0.80/1000) = 25 panels
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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