To keep it simple, let's break down what contributes to the total load of a PV system: Solar panels – Typically weigh between 10-15kg per square metre, depending on the make and model. . Dead load: This is the weight of permanent materials on the roof—structural components, insulation, and roofing materials. Roof materials like asphalt shingles or metal roofing provide different. . Roof load capacity is simply a measurement of how much total weight a roof can support per square foot. When calculating the necessary load capacity of a roof, you need to figure in what's known as the dead load along with live loads or environmental loads. It's measured in pounds per square foot (psf) and typically falls between 15-30 psf for most residential roofs.