Comment by aDyslecticCrow

Very situational on where it can be used, and requires some very careful cost calculations.

Ignoring the local effects of their construction, a damb breach is one of the worst man-made disasters possible. Mantinence and error margin must be very very carefully accounted for. There is a reason the world bank stopped funding them, and it wasnt purely enviromental. (Some badly managed projects led to expensive and dangerous situations)

So when relevant it's most powerful energy source avalible. But the list of preconditions and caveats is massive.