I live near a twin-lake hydro system that does just that. Every night the lights dim for a bit when the grid starts being used to pump water back up. http://e

I live near a twin-lake hydro system that does just that. Every night the lights dim for a bit when the grid starts being used to pump water back up. http://en.wikipedia.org/wiki/Smith_Mountain_Dam http://en.wikipedia.org/wiki/Smith_Mountain_Dam