The Kostolná hydroelectric power plant is the first power plant on the second (historically fourth) diversion channel. All the HPP´s on this channel are built for the same parameters, therefore they also have the same installed capacity of 25.5 MW each. A turbine flow is 90 m3.sec-1, i.e. 180 m3.sec-1 on aggregate for the plant, since each HPP has two sets each throughout the cascade.
Slovenské elektrárne operates 31 hydroelectric plants. Their combined output is 1,652.7 MW, representing approximately 38.4% of the Company’s total installed capacity. Majority of the installations is located on the Váh River cascade, or the longest river in Slovakia. On average, the hydroelectric sources generate 2,070 MW annually (consumption of pumped storage power stations excluded), or some 11% of the electricity produced by Slovenské elektrárne.
Because of their very variable power output and operational flexibility, hydroelectric plants are capable to satisfy the swiftly changing demands in the daily-load diagram, pairing nicely with the base load supply covered by nuclear power plants. Slovenské elektrárne has 736.6 MW installed in river hydropower plants and 916.4 MW in pumped storage power stations.