Hydroelectric dams require massive initial investments. True, dams generate cheap electricity, when the dams are eventually built. But building dams is incredibly costly. Actual costs for hydropower dams are almost always far higher than estimated; in a number of cases, the actual cost was more than double the estimated cost. The Itaipu Dam in South America cost $20 billion and took 18 years to build. This was 488% higher than originally estimated. [1] Given that there are cheaper alternatives than large-scale dams for renewable and accessible energy, dams aren’t worth it from an economic perspective.  [1] International Rivers, Frequently Asked Questions.