Solar Panel Power Output
P = G × η × A
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Formula
Description
The electrical power produced by a solar panel is the product of the incident solar irradiance, the panel conversion efficiency, and the panel area. Standard test conditions (STC) use 1000 W/m² irradiance at 25°C cell temperature with AM1.5 spectrum. Real-world output is typically 75-85% of the STC rating due to temperature derating, soiling, shading, and wiring losses. Panel efficiency ranges from 15-22% for commercial silicon panels, with premium monocrystalline cells reaching 24%.
Variables
- P — Electrical power output (W)
- G — Solar irradiance (W/m²)
- η — Panel conversion efficiency (0-1 or %)
- A — Panel area (m²)
Practical Notes
Panel output decreases about 0.3-0.5% per degree Celsius above 25°C for silicon cells. A 400W panel rated at STC might produce only 320W on a hot summer day. For system design, use location-specific irradiance data (peak sun hours) and apply a system derate factor of 0.75-0.85 to account for all real-world losses.
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