New True-up bill- another year on the books

Our yearly PGE bill for our electricity used that we did not produce-  The actually charges would have been $64.20 for the year, which would have been pretty good by itself.  But due to credits we get for being a grid-tied producer of electricity for PGE, that was knocked down to $15.38 for the year which is pretty close to free at that price. . .

Whats this? The next bill from PGE has a $31.00 climate credit which the bill says will be given to residential customers twice a year. That makes our electricity cost free for the year, and next year, and as long as we can keep our cost at or around $15 a year, free for the foreseeable future. . .