Ten of the largest hydroelectric producers as at 2014 (by country)

A hydro-electric station rarely operates at its full power rating over a full year; the ratio between annual average power and installed capacity rating is the capacity factor. The installed capacity is the sum of all generator nameplate power ratings.

Reference 1: Annual hydroelectric production (TWh), Installed capacity (GW), Capacity factor and % of total production.

Reference 2: China, Canada, Brazil, United States, Russia, India, Norway, Japan, Venezuela and France.

Source: http://en.wikipedia.org/wiki/Hydroelectricity