Standard Solar Panels: Most residential solar panels produce between 30 to 40 volts under standard test conditions (STC). What Is Solar Panel Voltage? Voltage, in the context of solar panels, refers to the electrical potential difference. While nominal voltage is the standardized voltage that's used to classify solar panels (usually, 12V, 24V, or 48V), the actual operating voltage of a solar panel is different. It's the voltage generated by a solar panel in real-time, and is highly influenced by environmental factors such as solar.