The Madunice hydroelectric power plant is located downstream the Sĺňava reservoir, which was artificially built in the Váh river bottomland. Similar construction conditions prevailed later on in building the Gabčíkovo water work. A major role in building the Madunice water work was played by the protection of spa springs in Piešťany. Curative springs and the formation of curative mud were not put into jeopardy, their even increased, so it was possible to substantially increase the number of annually treated patients. There are three sets having a turbine flow of 92 m3.sec-1 each installed at the Madunice HPP. The discharge channel empties near the town of Hlohovec into the Váh river.
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.