Photovoltaic panel grade classification table There are 4 levels of quality of solar silicon cells, called "Grade" - A, B, C, and D. Elements of different classes differ in their microstructure, which in turn affects their parameters and longevity. Get insights to make informed decisions for your solar project. Solar panels are graded into categories A, B, C, and D based on their quality, and the cost differences between these grades can be. Photovoltaic (PV) glass is the backbone of modern solar panels, directly impacting energy conversion efficiency and system longevity. A good solar company will have strict standards and a well-defined grading system the employees understand. Grade A ave some visual defects that do not affect performance.