On average, a 10-watt solar panel under optimal sunlight can generate approximately 40 to 60 watts-hours (Wh) per day. Estimate daily, monthly, and yearly solar energy output (kWh) based on panel wattage, quantity, sunlight hours, and efficiency factors. Losses come from inverter efficiency, wiring, temperature, and dirt. Increasing panel count or choosing higher wattage. Quick answer: A modern 400W solar panel produces about 1. residential median of 5 peak sun hours. For detailed assessment, it requires an understanding of how these factors interact over time. 83 by NREL PVWatts v8 default — or 0. 77 if you want a conservative. Peak Sun Hours (PSH) is the equivalent number of hours per day when solar irradiance averages 1000 W/m². PSH depends on location and season.