The best thing to use to clean solar panels is a soft-bristled brush and a mild soap solution. A mild soap solution can effectively remove dirt, dust, and grime from the surface of the solar panels, while a soft-bristled brush can help to scrub away the buildup without causing scratches. Avoid using abrasive cleaning materials, high-pressure water, or harsh chemicals, as they can damage the panels and reduce their efficiency. In addition, it is important to not walk on the panels as this can cause them to crack or become damaged. For best results, it is recommended to clean solar panels once or twice a year, or more frequently if they are located in an area with high levels of pollution or dust.