An energy system in a country has complex impacts on its economy. A retrenchment of energy supply influences economic activity such as distribution and saving of energy, as well as changes in technology to emphasize energy efficiency. Despite the advantages of hydropower developments in power generation over the past decades, highly controversial issues due to various social and environmental concerns are still debatable. A challenge for hydropower developers and operators, as well as government planners and regulators, is to develop tools that promote good practice and sustainable hydropower projects in energy security. In the future, both the scarcity of water and the cost of energy will likely to become limiting factors for economic and population growth, particularly in Malaysia, where the population is projected to grow dramatically. Various climate change models suggested that clean water supplies may decrease significantly. Therefore, integrated planning between the energy and water sectors will be essential to meet the rising demands of both resources. The purpose of this study is to review and identify the method that can deal with historical data and current practices at the hydropower plants to predict future electricity production due to the predicted water used in hydropower plants at the study areas. Various available methods to forecast water used and the electricity generated in hydropower plants have been identified and discussed in this paper.