In terms of solar energy output, when is STC measured?

Standard Test Conditions (STC) are used to measure the output and efficiency of solar panels under specific conditions that facilitate a consistent comparison across different products and technologies. STC is defined as the solar energy output measured under peak sunlight conditions, which includes a solar irradiance of 1000 watts per square meter, a cell temperature of 25 degrees Celsius (77 degrees Fahrenheit), and an air mass of 1.5.

Measuring at peak sunlight conditions ensures that the data derived from different solar panels can be effectively compared and understood, as it represents an ideal scenario where solar energy production is maximized. This standard is critical for consumers and manufacturers in assessing the performance of solar technology.

The other conditions presented do not reflect the environment under which solar panels are designed to operate most effectively. Average operating temperature can vary based on numerous factors, nighttime offers no solar output, and overcast conditions diminish sunlight availability, all of which deviate from those peak conditions necessary for STC measurements.