Choose a solar combiner box by checking string count, voltage, current, protection, enclosure rating, and room for future expansion. You also need to match the box to your system voltage, current, protection setup, installation. A solar combiner box is a crucial component in solar energy systems, designed to consolidate the outputs of multiple solar panel strings into a single output that connects to an inverter. In this article, we'll walk you through how to choose the right PV combiner box for your project. In practical project terms, the box does more than combine.