The short answer: most modern solar panels produce between 1. That typically works out to about 36–75 kWh per month per panel, depending on sunlight, orientation, and the efficiency of solar. 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. This tool allows users to quickly estimate how much energy a solar panel system can generate daily, monthly, and yearly. It's easy to use, requires just a few inputs, and provides accurate projections that can help you make informed decisions about your energy needs and return on investment (ROI). 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. solar installer uses is kWh/day = kW × PSH × derate, where the derate factor is 0. 83 by NREL PVWatts v8 default — or 0. A 400-watt panel can generate roughly 1. 5 kWh of energy per day, depending on local sunlight. household's 900 kWh/month consumption, you typically need 12–18.