Solar panel wattage in Thanjavur Sri Saravanas Agencies Solar panel wattage, also known as rated power or peak power (Wp), is a crucial specification that indicates the maximum electrical power a solar panel can produce under ideal, standardized test conditions. It's measured in Watts (W). Solar panel wattage is determined under Standard Test Conditions (STC) in a laboratory setting. These conditions are designed to allow for a consistent and fair comparison between different solar panels, regardless of their manufacturer.