It's economical to build a small amount of battery storage, enough for a few hours. For longer term issues, when things are dark and not windy for a long time,

It's economical to build a small amount of battery storage, enough for a few hours. For longer term issues, when things are dark and not windy for a long time, I'm not aware of any long-term plan. States like California are handling it by keeping old fossil fuel plants going for longer, and importing power from neighboring states.