Not to be too picky but it is actually the swings in supply they can't handle. Demand is inelastic and pretty much constant in the near term. The problem is th

Not to be too picky but it is actually the swings in supply they can't handle. Demand is inelastic and pretty much constant in the near term. The problem is that the clouds roll in, supply from solar drops off, conventional gen must compensate because the demand is pretty much constant and price insensitive. When the clouds roll-out the dispatchable gen has to back down so the wires don't melt. There are a bunch of concerns with this: generators often don't like being turned on and off, the generators often can't get paid enough to be there when they are needed, they often can't just be turned on and off (more of a problem for steam), and these peak shaving plants are expensive to fuel, burn dirty fuel, and burn it inefficiently.