A hydropower plant can provide up to 90% efficiency throughout the year. This is generally applicable to the power plants in association with large dams. This is because, large turbines can be installed in large dams, and these dams have a strong flow of water consistently. So, irrespective of the seasonal changes, the annual efficiency of around 85% to 90% can be achieved. The larger the dam, the better is the efficiency of hydroelectricity.