PG&E HATES, HATES, HATES people having solar, so they developed a system to punish them.
If you generate more power than you use, the "excess is a GIFT to PG&E (by law, a law sponsored by and paid for by PG&E).
If you use more power than you generate, they bill you for an entire year's worth of power in one lump. Mind you, they could bill you every month, they know to a fraction of a cent how much it is, but they'd rather punish you with a huge annual bill.
After the first year of THE BIG SURPRISE, I started paying 1/12 of the expected lump every month. The microsecond I get ahead on my PG&E bill, I start getting a THIS IS NOT A BILL DO NOT PAY notice mailed to me detailing my gas expense, the fee for having an electric meter and every charge except the actual electricity, and a notice of the positive balance.
No return envelope, of course.
I cut them a check, enclose the notice and mail it in a non-standard sized envelope...
That all sounds like a raging pain.