When Are String Inverters Not Recommended for Use?

System Design Limitations

String inverters are optimized for high-efficiency performance in fully sunny conditions. However, when a significant portion of the array is shaded, the entire string’s efficiency drops, leading to reduced overall system production. This is because string inverters are not capable of isolating shaded panels, forcing the entire string to operate at the lowest efficiency of the shaded panels. For example, if 20% of the system is shaded, the entire system’s efficiency may drop by 10-20%.

Micro-Inverter Advantages

Micro-inverters, on the other hand, can isolate shaded panels and continue to produce electricity from the unshaded sections of the array. This makes them ideal for systems with high levels of shade or irregular rooflines. For instance, a system with 20% shade can still achieve up to 80% of its maximum capacity with micro-inverters, compared to 50-60% with string inverters.

Cost and Complexity Considerations

While micro-inverters offer advantages in shaded systems, they also come with increased costs and complexity. System designers must consider the trade-offs between upfront costs, system efficiency, and maintenance requirements when deciding between string inverters and micro-inverters. In general, micro-inverters are recommended for systems with high levels of shade, complex rooflines, or high-efficiency requirements. However, string inverters remain a cost-effective and efficient solution for fully sunny conditions.