The specific wattage of an 11-volt solar panel generally falls within the range of 10 to 200 watts, contingent upon its design and specifications. Solar panel wattage is calculated using the formula: Watts = Volts x Amperes, indicating that both voltage and current are influential factors in determining watt output. Sunlight intensity: Output drops by 20-40% on cloudy days. Panel angle: A 30°. Quick answer: A modern residential solar panel measures roughly 66–82 inches long, 40–45 inches wide, and 1. 6 inches thick, weighs 40–55 lb, and produces 350–460 watts. Portable 100 W panels are about 42 × 21 inches. This doesn't mean they'll produce that amount all day, output varies with weather, shade, and panel orientation. Over a sunny day, it can make about 1.