Easy. US puts panels, turbines and batteries everywhere connected in big grid. Grid is big enough that something is always generating, and batteries smooth out the curve. Power is priced dynamically. Cheap solar at noon? Do big work. High demand in evening? Discharge battery. Power is always available, but cost goes up and down. Daily, god willing.
In theory that works as long as you're willing to let the price reflect actual supply and demand even when the difference is very large, e.g. it has been cloudy and still for a couple weeks so the batteries are low and then you get a hot summer day or cold winter night with a lot of demand. No problem, we'll just set the price to "high enough to get people to stop cooling/heating their buildings" and the market will clear. But people aren't going to like that.