5A solar panel generates 50 watts of power (20V multiplied by 2. 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. 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. This is your typical voltage we put on solar panels; ranging from 12V, 20V, 24V, and 32V solar panels. How to use this calculator? Solar panel output: Enter the total capacity of your solar panel (Watts).