A study of 245 large dams carried out at Oxford University shows that big hydropower is uneconomic. Actual costs are typically double pre-construction estimates - and have not improved over 70 years.

 

Researchers at Oxford University have found that planners and policymakers systematically underestimate the costs and time required to implement large dam projects.

 

The actual costs of large dams were 96% higher than the estimate, on average, and implementation took 44% longer than scheduled. The new report thus explicitly states that large dams are not economical: "We find that even before accounting for negative impacts on human society and environment, the actual construction costs of large dams are too high to yield a positive return."

 

The study is based on the most comprehensive economic analysis of large dams ever undertaken. "Large dams" refers to dams with a wall height in excess of 15m.

 

The study, which is based on a representative sample of 245 large hydropower dams built in 65 different countries between 1934 and 2007, concludes that cost and time overruns have not improved over time.