But renewable is already cheaper than fossil fuels. Why don't we see this already?
Notice several caveats: electricity, not heat; daytime, not nighttime; only for some places on the globe.
Most energy use doesn't use electricity. It's one thing to replace an average-16%-efficient internal combustion engine with electricity and another to replace a 96%-efficient condensing boiler.
Electric heat is rare since it’s inefficient (thermodynamics) and thus expensive but it’s used in applications where you need precision temperature control.
Of course if solar and batteries got cheap enough you could just say F it and use electric resistance heat everywhere. Time your peak production to coincide with mid day when solar is at peak.
We could take all suburban United States off of fossil fuel heating with solar heating. But that would require planning up front and cost some powerful people money, so we can't.