The short answer: Yes, for most solar systems, a combiner box is essential. It depends entirely on your specific setup. This overview will clarify the role of a combiner box, explain when it becomes a critical safety. The solar combiner box is an electrical device in a photovoltaic power generation system used to combine the direct current generated by multiple solar modules or strings into one output, which is then sent to the inverter. Collects multiple string currents, reducing the number of cables.