That's because solar usage has created a "duck curve" I would imagine it would be even more unfair to make normal energy users pay for that: https://youtu.be/YYLzss58CLs
This is why California is moving to Time of Use rates (TOU) in late 2019/2020 (depending how they push off the date due to IT challenges).
It's really more about corruption than anything else. PG&E still charges vastly increased rates in California despite huge drops in wind and solar prices.
That is probably a bit more complex and a bit harder than you are implying. Attempts to interconnect the main grids are large projects that take many years to do. The Tres Amigas SuperStation is an attempt to unite the Eastern Interconnection, Western Interconnection) and the Texas Interconnection). First announced in 2008. It will carry 5 GW of power which seems like a lot until you consider that the US uses about 4,000 terawatt hours per year,
https://en.wikipedia.org/wiki/Tres_Amigas_SuperStation
>...It's really more about corruption than anything else. PG&E still charges vastly increased rates in California despite huge drops in wind and solar prices.
PG&E gets maybe 10% of their power from solar, Much of that power they have to pay the RETAIL rate for since rooftop solar is heavily subsidized - of course it is going to have to increase what it charges other people.
The problem is that utilities want it both ways. They want to charge you peak usage despite the fact that "peak" generation is actually becoming one of the cheapest times for power.
If they allowed free-market pricing in that power they could easily find a use for "curtailment" -- people would crank their ACs or charge their cars if the price kWh dropped below a certain point.