How much electricity can solar panels generate in a day? This depends on the STC or PTC rating of the panel; STC represents standard test conditions and represents the power generated by the panel under ideal conditions. Manufacturers test panels under conditions called solar peaks, when the sun Z is bright, which usually lasts about four hours. The sun’s peak is calculated as 1,000 watts of sunlight per square meter of the panel’s surface. The STC rating is the degree to which peak sunlight is converted into energy.

A panel with an STC rating of 175 watts converts one hour of sunlight to 175 watts. Multiply the STC rating of each panel by the number of panels and you will know how much energy the array produces under peak conditions. You then multiply that number by the number of hours of peak sunlight the panel gets each day, and you’ll know how much energy the solar panel system produces. If each panel has an STC rating of 175 and you have 4 panels, then 175 x 4 = 700 watts. Thus, 700 x 4 = 2800 watts is generated during peak daylight. Note that the solar array also generates power in lower light, so the total energy generated during the day in this example will be higher than 2,800 watts.