In the 1930s, Allgemeinen Elektricitätsgesellschaft (AEG) and Alpen-Elektrowerke AG (AEW) developed projects for power plants near Malta. Plans of the Österreichische Bundesbahnen followed after 1945. In 1952, Österreichische Draukraftwerke AG (ÖDK) carried out water and energy-related tests and created a plan for the utilisation of the Malta and Gößbäche with a three-stage power plant group. A dissertation written in 1956 at the technical university in Graz by Erich Magnet with the title "Winter Storage Plant Inner Maltatal-Kolbnitz" was used by Österreichische Draukraftwerke AG and proved to be very important for the development of the project.

The water rights negotiations for the Malta upper stage and Malta main stage power plants took place in 1964. The approval of the water authorities was granted in 1965. Heavy protests, especially from the Austrian Society for Nature Conservation, followed when the project area lost its nature conservation status. The conservationists called for the erection of nuclear power stations as an alternative to storage power plants. The detailed planning commenced in 1971 following the positive construction decision.

In addition to covering demand peaks, it was required that the power plant group Malta must, at all times, be in a position to provide reserve power for a failed nuclear power plant. The earlier-than-expected issuing of the building decision and the new requirements created major challenges for the planning and construction departments. In addition, the first machine unit for the main stage was to be commissioned two years earlier than expected on 1 December 1978. The planning was carried out, inter alia, by Construction Director Kurt Baustädter, Rudolf Mußnig, Kurt Landl, Heiner Ludescher and Georg Lichtenegger from Draukraftwerke AG. External planners, such as the civil technology company Ehß, were also engaged. The architectural work was carried out by Rudolf Nitsch from Klagenfurt.

After a series of geological tests, the final location for Rottau power plant was fixed in 1973. The excavation pit reached a depth of approximately 30 metres below the valley basin and 25 metres below the groundwater level. Extensive safety measures were necessary to prevent the penetration of groundwater. The first machine unit was commissioned in Rottau power plant in late autumn 1976. The storage pumps were commissioned in summer 1978. The capacity of 730,000 kW corresponds to the capacity Zwentendorf nuclear power plant would have had.

Open-loop Pumped Hydro Storage