> Price goes up slightly. How much of a swing in pricing are we talking about here? Because that storage mechanism is maybe 80% efficient. So the price swing

> Price goes up slightly. How much of a swing in pricing are we talking about here? Because that storage mechanism is maybe 80% efficient. So the price swing would have to be at least that big to break even. And in that case, if they are helping to smooth out swings in demand that are that large... Sounds like they're providing a valuable service. https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity#Economic_efficiency https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... EDIT: Keep in mind that electricity is entirely fungible. This is no different than the Swiss turning on a power plant when prices are higher. Except it would probably be too expensive to have a power plant just sitting there idle when the price isn't "high enough".