Net billing slashed export credits for most of the year — but during 1-2 hours a day in August and September, SDG&E pays $1 to $3.50 per kWh for power sent to the grid. That's up to 8x their own retail rate.
A well-designed solar + battery system charges itself on nearly-free sunshine all year, then cashes in during exactly those desperate late-summer peak hours. These credits are a major reason the best true-up date is July 1st (right before peak sun), and why proper system design in the net billing era can still get you to a ~$0 monthly bill. It takes software, your Green Button usage data, and a designer who actually cares. But the window is there.