Usually, 5V solar panels produce anywhere from 0. 5 to 3 watts, sometimes even more, especially if designed for specific high-efficiency applications. These panels are often used in small applications such as charging batteries or powering low-energy devices, 3. It starts off with the following equation: Where: electricity consumption (kWh/yr) – Total average amount of electricity you use annually. Found on your utility bill, and solar hours per day – Average hours of direct. . The fundamental formula for calculating solar panel wattage is: Wattage = Voltage × Current When applied to solar panels, this can be expressed as: Solar Panel Wattage = Vmp × Imp Where: Vmp represents the voltage at maximum power point, indicating the optimal voltage level at which the panel. . Estimates the energy production of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations. Operated by the Alliance for Sustainable. . How many watts is a 400W solar panel? The number in the panel's name is its rated wattage. But remember, that's under test conditions. Renogy 200W Portable Solar Panel, IP65. .