We're almost there with PV Solar price/performance.

[Jester]

Though to speak a little more directly to Jester's point. Solar and wind will at times be offline at the same time, but wind can be 24/7, and of course when solar is offline demand is usually lower. There are even times when solar isn't online where wind will be more available, such as storms. Though that requires wind generation to be more variable than it currently is. I know some turbines have to be shut off or heavily governed if the wind speeds get too high.

Convenient though that is, it doesn't solve the problem. Even if 99% of the time, when solar is down, wind is up, and vice versa, that's still 1% of the time when both are down. (Warning: Numbers pulled out of nowhere for sake of argument!) When that happens, we still need 100% of our grid capacity to be fulfilled through some other means - at the same cost in backup capacity, either spare plants or batteries, because supplying that load once a year requires roughly the same amount of spare capacity as doing it every day. Some brownouts here or there is bad, but total output dropping to near zero because it's a miserable, windless day? That's going to shut everything off at once.

-Jester