Serbia’s planned €2.6 billion Iron Gate 3 pumped-storage hydropower project, known as Đerdap 3, faces critical questions over Danube water availability, Romanian cooperation and investment viability.
The project is currently being assessed at up to 1,800 MW, while earlier EPS concepts envisaged capacity of 2,400 MW and approximately 578 million cubic metres of storage. The facility would store surplus electricity and generate power during periods of high demand, providing grid balancing and energy-storage capacity. Its commercial performance will depend on operating conditions within the shared Danube river system.
Danube Management and Romania’s Energy Security
The existing Iron Gates complex has approximately 2.9 GW of combined hydropower capacity. Serbia’s EPS operates 1,140 MW at Đerdap 1 and around 270 MW at Đerdap 2, while Romania’s Hidroelectrica operates approximately 1,166 MW at Porțile de Fier I, alongside additional capacity at Porțile de Fier II and Gogoșu.
Further downstream, Romania’s Cernavodă nuclear power plant, with approximately 1.4 GW of gross operating capacity, relies on the Danube for cooling. During the 2026 drought, both reactors were forced to shut down because of low river levels, highlighting the importance of reliable water supplies. Although pumped storage largely recirculates water, initial reservoir filling, pumping schedules and release timing could affect downstream flows. Restrictions during droughts could limit the plant’s ability to charge when electricity prices are low, directly affecting its revenues.
Romanian Cooperation Could Determine Operating Rules
Romania could seek conditions covering reservoir filling, drought-related pumping restrictions, minimum downstream releases and strategic water reserves. Existing bilateral arrangements governing the Iron Gates system, alongside environmental and transboundary-water requirements, could give Bucharest substantial influence over the project’s operating regime. Đerdap 3 could also benefit Romania. Water stored before a drought could be released during low-flow periods, potentially supporting Cernavodă’s cooling requirements while generating electricity.
EPS has identified this possibility, but implementation would require agreements on reserved water volumes, release decisions and compensation. Water held for Romanian energy security would not necessarily remain available for unrestricted electricity-market trading.
Černi Institute and Bechtel–Enka Advance Preparation
The Jaroslav Černi Water Institute, part of Millennium Team, is leading the consortium responsible for early planning and technical documentation. Its work will establish key assumptions concerning hydrology, reservoir design, environmental impacts and investment costs.
The Bechtel–Enka consortium has qualified for negotiations on further project and technical work. However, qualification does not constitute a final construction award or financial close. Independent technical review will be important before major commitments are made, particularly if Romanian requirements or revised hydrological and geotechnical assessments necessitate design changes.
Investment Returns Depend on Realistic Operating Conditions
At an estimated €2.6 billion, Đerdap 3 must compete with alternatives such as battery storage, grid reinforcement, interconnections and upgrades to existing hydropower plants. At an illustrative 80% round-trip efficiency, electricity purchased at €50/MWh would cost €62.50/MWh in recovered electricity before operating expenses, financing and capital recovery. Restrictions on pumping could further reduce profitable operating cycles.
Serbia’s feasibility assessment must therefore incorporate realistic drought scenarios, Romanian water requirements and enforceable operating rights. The decisive question is whether the project can deliver sufficient returns under these constraints to support financing and eventual construction.
