30 percent roof rule

https://direct-wiki.win/index.php/Should_You_Repair_or_Replace%3F_The_30_Percent_Roof_Rule_Explained

The 30 percent roof rule is a practical guideline for solar panel installation, suggesting that panels should cover no more than 30% of a sloped roof's surface to ensure proper structural load distribution and avoid overloading the roof. It also helps maintain access for maintenance and reduces shading issues. This rule of thumb keeps installations safe and efficient without overwhelming the roof's integrity or aesthetic balance.