AFAIK, most home solar is not set up this way. You don't use the energy from your solar panels. The solar panels feed directly into the grid, and your usage comes directly out of the grid.
So if you use 100kwh, and generate 100kwh, then you will pay 100kwh at retail rate, and receive 100kwh at wholesale rate.
The Solar out actually runs your meter backwards, so does actually reduce the amount the meter shows you owing to charge you at the retail rate. There is no metering present to make it possible to charge you for the 100kwh you used at one rate, but then you pay you for the 100kwh you generated at a different rate. The electricity you generate runs the meter backwards, and reduces what you are charged for consumption -- which monetarily means you are "being paid" for it at the retail rate.
But if your meter goes negative in a given time period, they can tell at the meter you actually generated more than consumed, and could pay you out a different rate for that. (Or as OP notices, in some places, they allow you offset your use, but don't actually pay out for net negative at all. )
This is why the metering is called "net", it's your "net" use, consumption minus generation. I believe that's how it works for my friends here in Baltimore who have solar panels.
Are there other places in the USA where they install more sophisticated metering capable of separately metering out and in, and charge different rates for it?
Or, anyway, since we're talking about California, if anyone wants to clarify how it actually is going to work in CA, rather than speaking in hypotheticals based on our theoretical understanding of how things work, that would be even better!
But I agree with the message several posts up. The old net metering was a subsidy and I understand it going away. It makes sense to me at a technical level that you would be billed your fine-grained net usage, so if your solar supports your daytime load then you didn't consume power, but you can't expect daytime excess to 1:1 cancel your nightime grid load, unless you install local batteries to time-shift your own power.
The old net metering did that. People generate excess during the day and consume power at night from the grid and expect it to all cancel out.
Do you have details on how home solar is or will be metered in California, with regard to credits for power generated, and if it will be different depending on whether it's "net negative" or not?