Hydropower is the leading renewable source for electricity generation globally, supplying 71% of all renewable electricity. Reaching 1,064 GW of installed capacity in 2016, it generated 16.4% of the world’s electricity from all sources.

Hydropower is the most flexible and consistent of the renewable energy resources, capable of meeting base load electricity requirements as well as, with pumped storage technology, meeting peak and unexpected demand due to shortages or the use of intermittent power sources. There are many opportunities for hydropower development throughout the world and although there is no clear consensus, estimates indicate the availability of approximately 10,000 TWh/year of unutilised hydropower potential worldwide.

At the end of 2015, the leading hydropower generating countries were China, the US, Brazil, Canada, India and Russia.

Hydropower capacity is often categorised as ‘gross theoretical capacity’, the capacity of hydropower generation possible if all natural water flows contained as many 100% efficient turbines as possible; ‘technically exploitable capacity’, the amount of gross theoretical capacity possible within the limits of current technology; and ‘economically exploitable capacity’, the capacity possible within the constraints of current technology and local economic conditions.

There are three types of hydropower stations: ‘run of river’, where the electricity is generated through the flow of a river’; ‘reservoir’, where power is generated through the release of stored water; and ‘pumped storage’, where stored water is recycled by pumping it back up to a higher reservoir in order to be released again. Hydropower facilities installed today range in size from less than 100 kW to greater than 22 GW, with individual turbines reaching 1000 MW in capacity.

Hydropower data on installed capacity (MW) and annual output (GWh) is sourced from the International Hydropower Association (2016) and represents the values at the end of year 2015.