For most standard solar panels, which measure about 1. 6–2 meters in length, four mounting brackets is the general rule—two brackets on each side. This setup provides balanced support while keeping installation simple. Using the right number of. Here is a simple equation that will help you estimate the number of solar panels needed for differently-sized solar systems: Number Of Panels = (Solar System Size In kW × 1000) / Solar Panel Wattage For example, if you want to install a 3kW system, and are wondering how many 300-watt solar panels. When planning a solar energy project, accurately estimating the number of racking system components—such as rails, clamps, support legs, and connectors—is essential. Basic Bracket Requirements Solar.