Under previous net metering plans, retail customers were compensated at their retail rate for excess solar power. Under NM3.0, you are compensated at some wholesale rate that does not include transmission and other fees in the retail rate, there is something like a 75% drop in the rate paid. Also under NM3.0 the rate changes hourly and based on time day and time of year.
What this does is incentivizes home battery systems. Where you store your excess power and use it in the evening. Most of the battery systems for California will automatically chase the best times/rates to dump power back to the grid under NM3.0. There will be times even with battery systems that you'll pull power from the grid, these will result in a positive bill every time because you can't have a negative balance, if you go to zero on your bill you start donating power to the grid.
It used to be that net metering would help pay for the solar system over time. With the right size of system you could have a $0 power bill, but never negative.