The efficiency of a 520W solar panel depends on its area, materials and design. Generally speaking, high-efficiency solar panels can achieve conversion efficiencies of 20% or more, while low-efficiency solar panels may only have conversion efficiencies of around 10%. Therefore, the actual output power of a 520W solar panel will typically be between 100 and 400 watts, depending on the actual efficiency of the panel and environmental conditions. It is worth noting that the output power of a solar panel is also influenced by many other factors, such as light intensity, temperature, and shading. Therefore, it is best to consult a professional before purchasing to confirm its efficiency and suitability.