This year, our negative bill that we never get paid for wasn't as negative as usual. This was mostly because we used 800Kwh more, partially because some of my computer stuff wasn't shutting down as often as it should have.
On the other side, PG&E doesn't make it so like I should care since it's just a difference between 2 negative bills for which I'll never see a penny anyway.
If I count 20c/Kwh with the different tiers, the solar panels saved us maybe $12000 so far, or getting to a half of the price we had to pay ($26k). Not bad...