Voltage Drop

Voltage drop is the reduction in electrical voltage that occurs as current flows through wires over a distance. In solar installations, excessive voltage drop means energy is wasted as heat in the wiring rather than being delivered to the inverter or electrical panel.

The NEC recommends keeping voltage drop below 3% for any individual circuit and below 5% for the total system (from panels to the point of connection). Factors that affect voltage drop include wire gauge (thickness), wire length, current flow, and temperature. Longer wire runs between the solar array and the inverter require thicker (lower gauge) wire to keep voltage drop within acceptable limits. This is especially important for ground-mount systems, where the array may be 50–200 feet from the house. Excessive voltage drop reduces system efficiency, wastes energy, and can cause inverters to underperform or shut down. Your solar installer calculates voltage drop during system design and selects appropriate wire sizes accordingly. Using properly sized conductors adds a small cost but ensures your system delivers the maximum energy from your panels.