A 9kw solar system can generate 35 to 45kWh of electricity per day and requires 30 300W solar panels. After the tax credit, it costs approximately $15,750 and $22,050. A 9kW solar system, under optimal conditions, can produce a significant amount of energy. 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. 83 by NREL PVWatts v8 default — or 0. 77 if you want a conservative. 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. residential median of 5 peak sun hours. Over a sunny day, it can make about 1.