hydroelectric power is a means of making electricity without burning fuel. hydroelectric power supplies about 715,000 mwe or 19% of world electricity (16% in 2003). large dams are still being designed. apart from a few countries with plenty of it, hydro power is normally applied to peak load demand because it is readily stopped and started. nevertheless, hydroelectric power is probably not a major option for future energy production in the developed nations, because most major sites within these nations are either already being exploited or are unavailable for other reasons, such as environmental considerations.