At full sun, it makes 400 watts. 6 to 2 kWh, depending on conditions. Free solar panel power calculator to estimate energy and power output. 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. The testing is very precise: it requires exactly 1000 watts per square metre of light that hits the glass surface, while the temperature stays at a cool 25 degrees Celsius with a light spectrum that copies real sunlight. Like this the shown number is only the best possible case not what you will. Quick answer: A modern 400W solar panel produces about 1. residential median of 5 peak sun hours. A 10 kW system produces about 42 kWh/day. 70. A PV Watt Calculator is a tool that estimates the amount of electricity (in kilowatt-hours, kWh) your solar power system will generate based on: System Size (kW): The total capacity of your solar panels. System Efficiency. Caution: Photovoltaic system performance predictions calculated by PVWatts ® include many inherent assumptions and uncertainties and do not reflect variations between PV technologies nor site-specific characteristics except as represented by PVWatts ® inputs.