How much money does it take to maintain a hydroelectric dam?

Answer 1

answ2. Hydroelectric dams are temporary features. They will eventually fill up with gravel and silt from the river. This is very expensive to remove.

Otherwise the maintenance is things like removal of debris that may damage the turbines. The actual maintenance of turbines and generators is small - occasionally bearings need replacement and so on. Pretty minimal overall.

Hydroelectricicity is expensive to install, but the annual running costs are very small.