Solar load calculation determines your energy needs to size a solar system, focusing on daily Watt-hours (Wh) by listing appliances, their power (Watts), and usage time (Hours), then factoring in real-world inefficiencies, local sunlight (Peak Sun Hours), and backup days for cloudy weather to find required panel wattage and battery capacity. It's a crucial first step to ensure your system reliably meets your energy demand, preventing under-sizing.