Thanks hayhayhay, That would make sense, but my read of NEM-2 is that PG&E takes a look, once per year, at total generation and consumption, and then bills or refunds to true-up. I'm not understanding if they consider when the "excess" consumption took place or if/how they decide which kWh are the excess ones that they bill me for.
Welcome to solar! Congratulations on getting in before they killed NEM2.
PG&E does consider the time of consumption and of generation. Consumption is charged at the retail rate per kWh based on time and season, and generation is credited at the same retail rate minus a small fee of about 3¢ per kWh for "Non Bypassable Charges". The total monthly charges and credits are not billed monthly, but instead are accumulated in your account. You are billed around $10 each month for what they call "Minimum Delivery Charges", essentially their cost of the meter and billing, but in your true-up, this amount may be credited against the accumulated total amount you owe for the year.
At the end of the year, what you have already paid, around $120, is subtracted from the accumulated charges and credits. If you still owe, they bill you the difference as a "True-Up Adjustment". If your balance says they owe you, they keep it, sorry.
There are a few other possible outcomes because of "minimum" changes for NBC's or minimum "energy charges" and those monthly Minimum Delivery Charges. And in the event that you actually export more kWh than you import, you are considered a Net Generator and are credited at a small rate for the excess kWh. I got a $4.00 credit once!
To simplify, you pay ~$10 per month plus a yearly mystery bill. You monthly bill will show but not ask you to pay the accumulating totals. Typically your year end adjustment will be the largest of the accumulated totals minus what you have already paid, but not less than zero.
The concept is that you can run you meter foreward and backward, essentially loaning or borrowing power to and from the grid with the grid acting like a giant battery. This lets you, in effect, use your own solar at night, and to bank your summer excess to use in the winter. But because PG&E needs juice during peak time and has excess at night, they use the time of use rates to encourage import at night and export during peak times, and to accomplish this they apply the time-of-use rates to your in and out flows. But they do not credit retail for any more kWh than you bought from them at retail. They are not buying you juice, but rather giving it back to you when you need it.
I hope this helps. It is a very clever system because it is revenue neutral for PG&E, but lets you install only enough solar to supply your
average needs over the entire year, day and night, summer and winter. But the details do get a bit complicated.