156 Mono Solar Cell A-Grade 156 mono solar cell : efficiency 15.60% ~ 16.99% ( 3.73 ~ 4.06Watt ) B-Grade 156 mono solar cell : efficiency 15.60% ~ 16.99% (3.73 ~ 4.06 Watt ) , Surface Defect C-Grade 156 mono solar cell : efficiency 15.00% ~ 15.59% (3.59 ~ 3.72 Watt ) D-Grade 156 mono solar cell : IREV2 or Big Surface Defect