[expatpat]

The point is to take power out and store it when it's not needed on the grid, so you can use it during peak-need times.

Analogy: your car battery stores energy during driving periods, so it's available for the heavy-current need when starting the engine. Your alternator-battery system loses energy, but it's still a big net value compared with hand-cranking the car engine, as in pre-WWII days.

[dila813]

Wouldn’t be better to just let less water out of a regular hydro dam?