The laws of physics tell us that the energy produced cannot be more than the energy use to produce it. You cant get nothin for nothin as they say. It is a simple energy transfer. The energy from the moving water is transferred to the turbine plus the losses due to friction, electrical losses etc. The biggest problem with this system is that most cities or towns dont have enough head pressure to make enough power to make it economical, although these days you would think it would make sense as the price of power has quadrupled in a short period of time. I have made my own power using pumped hydro for years, and that has certainly paid for itself, so you would think that the experts in the field could make it heaps more efficiently at a larger scale commercially, then again the way most of the country is run, maybe not........
