Solar Panel Rated vs. Actual Output – Why is it Lower?
Provides a thorough explanation why solar panels don''t perform at their rated output, and the difference between power output and efficiency.
Solar panels receive their ratings under specific testing conditions known as “Standard Testing Conditions” or “STCs”. These conditions serve as the industry standard for evaluating solar panels, making it easier to compare panels accurately. STCs replicate ideal operating conditions, including: And a “Solar Cell Temperature” of 25°C.
While real-world conditions typically reduce efficiency, there are rare cases where panels can exceed their rated output. In environments with cold temperatures, clear skies, high altitudes, and perfect sun alignment, a solar panel can generate more power than its stated rating.
For example, the nameplate from my solar panel specifies a Wattage output of 100W, meaning that the solar panel is capable of producing 100 Watts of power under ideal conditions. Manufacturers also provide an “Output/Power Tolerance” rating, showing how much the actual output can vary from the rated output.
Some panels' high power output rating is due to their larger physical size rather than high efficiency. If two solar panels have 20% efficiency ratings, but one has a power output rating of 350 watts and the other is rated at 400 watts, all that means is that the 400-watt panel is about 14% larger than the 350-watt panel.
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