A 30W solar panel typically produces approximately 120 watt-hours of energy per day under optimal sunlight conditions, which translates to a monthly output of around 3. 5 kWh of electricity per day, depending on various factors such as location, sunlight exposure, and efficiency. The daily output can vary based on seasonal changes, with summer often providing more energy than winter. Losses come from inverter efficiency, wiring, temperature, and dirt. Actual output. Quick answer: A solar panel's daily energy output is its kilowatt rating × peak sun hours per day × derate factor. 83 by NREL PVWatts v8 default — or 0. Estimates the energy production of grid-connected photovoltaic (PV).