STC

Science & Engineering abbreviation · Energy

STC
Stands forStandard test conditions
CategoriesScience & Engineering

STC stands for Standard test conditions, an energy abbreviation.

Laboratory conditions used to rate solar panels: irradiance of 1,000 watts per square meter, a cell temperature of 25 °C and a light spectrum corresponding to air mass 1.5. A panel's nameplate wattage and efficiency are measured at STC.

Example: The 430-watt rating applies at STC; on a hot roof the panel will typically produce less.

Usage notes

Real panels usually run much hotter than 25 °C in sunlight, losing roughly 0.3-0.4% of output per degree, so manufacturers also publish ratings under nominal operating conditions (NOCT or NMOT). Comparing panels at STC ensures a fair, consistent basis.

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