Here’s a nice and useful article I found on the important theme of solar panel grades.

Most times, buyers of solar panels keep hearing about grades of solar panels but most don’t have a clue of what these grades mean.

This article provides a detailed explanation – see here

Summary:

Grade – A normally means a panel has no visible defects and all the major possible defects are covered by manufacturer’s standard warrantyl.

Grade – B usually means the panel has some “cosmetic imperfections” or “cosmetic blemishes” of the above, but has the “same” electrical output as Grade – A.

Grade – C solar cells are those with a flaw that affects the power output, so the output power is somehow lower than A and B Grade cells, and the price is lowest.

Grade – D modules are generally considered unusable and thrown out by manufacturers.

Interesting indeed

Source