Posted: 27 November 2007

Large-scale hydro power supplies 20 per cent of global electricity, and is currently the largest source of renewable power. It is a 'clean' power source, in that it does not generate air pollution or carbon emissions, and has low maintenance costs, but in the industrialised countries it has nearly reached its economic capacity and it scope for expansion is very limited.

  • In the developing world, considerable capacity still exists, but large hydropower projects often face financial, environment and social constraints.
  • Hydropower is efficient: modern hydro turbines can convert as much as 90 per cent of the available energy into electricity. The best fossil fuel plants are only about 50 per cent efficient.
Energy costs diagram
Energy costs diagram
Figure shows fuel, maintenance and operating costs for fossil fuel steam plants, nuclear, hydropower and gas turbine generators. Credit: Wisconsin Valley Improvement Company

  • It is cheap: in the United States, hydropower is produced for an average of 0.85 cents per kilowatt-hour (kwh). This is about half the cost of using nuclear fuel, 40 per cent of fossil fuel and a quarter the cost of using natural gas.
  • Norway produces more than 99 per cent of its electricity with hydropower. New Zealand uses hydropower for 75 per cent of its electricity. Canada and the United States are the two largest hydropower producers. However, Norway has recently abandoned several big hydro projects for environmental reasons.
  • Hydropower provides about 12 per cent of the electricity in the United States - enough to serve the needs of 30 million residential customers.
  • In Pumped Storage hydroplants, off-peak electricity is used to pump water up to an upper reservoir.
  • In the past, hydropower stations were often built as a part of large dam projects. Due to the size, cost, and environmental impacts of these dams (and the reservoirs they create), hydro developments today are increasingly focused on smaller-scale projects.