"pyotr filipivich" wrote: Ah, "cost" - they charge extra for the
electricity delivered by
the pumped water. But does the amount of electricity produced equal
or exceed the amount consumed in the pumping?
^^^^^^^^^^^^^^^^^^^^^^^^^
The water keeps coming down the river whether you can use it or not. During
peak load periods there may not be enough water to meet their generation
needs. During the wee hours of the morning there is more water than they
can use. Pumping water uphill into a pond is like charging a storage
battery--you get to use it later.