To understand what the lie is, you need to know the purpose of a pumped-storage hydroelectric (PHS) power station. Like any power station, a PHS station produces electricity for consumers. It does so by converting the kinetic energy of flowing water into electricity. However, it has an additional purpose as indicated by the phrase "pumped storage."Perhaps if you had looked up the Wikipedia article about pumped hydro storage sites, you would find that there are precisely 9 of them in the USA with a total nameplate capacity of 13,612 megawatts. (This will go up by a few hundred MW as Ludington is upgraded with more advanced and efficient pump-turbines.) This is not what they can store (equivalent to gallons of gasoline); it's their maximum instantaneous output (equivalent to engine horsepower). Average US grid demand is on the order of 450,000 MW. All the PHS plants in the USA, running flat-out, can serve roughly 1.5% of average US grid consumption.
When more electricity is generated in the electrical grid than is necessary, it needs to be disposed off somehow. It can be burnt off, but a better solution is to find a way to store that electricity until it is needed. In a PHS, electricity is stored by using the extra electricity to pump water into a reservoir at a higher elevation. Later, that water can be released to produce electricity. It is basically a battery you can charge when you have extra power and discharge when you need more power.You can't generate more power than the grid needs, not for a significant time or fraction. The reasons why involve BSEE-level mathematics which you obviously don't have, but the point is that there are NO significant stores of energy in the grid proper except for the sheer mechanical inertia of its large synchronous rotating machines (both generators and motors). If you pump in power over consumption, those machines speed up past their rated speeds; a power deficit causes an underspeed. Too much of a deviation trips generating plants off the grid and causes a blackout. Generation must match load to a very high degree instantanously, and even more closely over time.
If a power station produces 100 GW every hour, no more, no less, would we say it is impossible for it to output 1,000 GW in a single hour? I would hope not. If the station's electricity wasn't needed for 10 hours, it might store up 1,000 GW.Aside from impoundment-fed hydro stations (both pumped and otherwise), the only stores of energy in powerplants on the grid are:
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