Wind and solar are now the cheapest sources of electric power. The problem is that they are not baseload generators. Their maximum production is not when there is maximum demand. That is why there is so much interest in various means of energy storage: batteries, pumped hydro, compressed air, (solid) gravity storage, thermal, etc. The California state government saw this problem coming several years ago and have been requiring utilities to plan ahead.

The UK has had several days this year when their entire electricity production came from wind, but they have the weather for it, rather like the high plains in the US.