With the launch of Mochovce Unit 4, Slovakia is moving to the very top of global nuclear energy. In terms of the share of electricity generated from nuclear power compared with the country’s total consumption, Slovakia will reach 77.5%, surpassing even France at 67% – long regarded as the symbol of nuclear dominance in Europe. This is a historic milestone that places Slovakia among the world’s most intensive users of nuclear energy, not only in absolute figures, but above all in relation to the size of its economy and the country’s needs.
Fuel loading marks the transition from the construction phase to the active commissioning of the unit. It will be followed by pre-critical tests, the first controlled fission reaction and a gradual increase in output up to synchronisation with the electricity grid.
Fuel loading is one of the most sensitive operations in the entire process of commissioning a nuclear unit and takes place under the strict supervision of the Nuclear Regulatory Authority of the Slovak Republic.
“The Nuclear Regulatory Authority of the Slovak Republic issued the decision authorising the commissioning of Unit 4 of Mochovce Nuclear Power Plant Units 3 and 4 after a thorough and detailed verification that all legislative conditions and technical requirements had been met. Inspectors of the Authority assessed the unit’s readiness to begin active testing in all areas under review, both by examining the submitted documentation and reports on the results of inactive tests, and through daily inspection activities on site during construction, equipment installation, functional testing and the verification of personnel readiness. A high level of nuclear safety remains an absolute priority also in the next stage of physical and power start-up testing.”
Marta Žiaková, Chair of the Nuclear Regulatory Authority of the Slovak Republic
Unit 4, with an installed capacity of 471 MW, will cover approximately 13% of electricity consumption in Slovakia. It complements Unit 3, which has been in operation since 2023 and, together with the other nuclear sources, significantly strengthens Slovakia’s ability to cover domestic consumption with its own production. If Units 1 and 2 at Mochovce and Bohunice Nuclear Power Plant are also included, nuclear sources already cover approximately two thirds of electricity consumption in Slovakia today.
Mochovce Unit 4 closes one of the key chapters in the development of Slovak energy. It is the moment when the long-standing efforts of thousands of people become tangible value for the country — stable, low-emission and price-predictable electricity. Mochovce 4 is a source of both professional and personal pride, and proof that even smaller countries and nations can achieve great things.
Branislav Strýček, Chairman of the BoD and CEO of Slovenské elektrárne
The Mochovce 4 project strengthens the energy security of Slovakia and the wider region. Nuclear energy remains a key stabilising element in Europe — it provides a significant share of low-carbon generation and helps balance fluctuations in renewable sources. Nuclear energy accounts for approximately 23% of electricity generation across the EU.
The Mochovce 3 and 4 project ranks among the largest private investments in Slovakia’s history, with total costs of approximately EUR 6.7 billion. Work on completion resumed in 2008, when Slovakia built on the original project and enhanced it with modern safety standards.
Unit 3 was synchronised with the electricity grid at the beginning of 2023 and gradually reached full output. The completion of Unit 4 therefore closes a project implemented across generations and today delivers its final result: a modern and safe source of electricity for Slovakia.
With a 66% share of total electricity generation in Slovakia, Slovenské elektrárne, a.s., is the country’s largest electricity producer. Following the closure of its last coal-fired power plant at the end of the first quarter of 2024, the company now produces all its electricity without direct CO₂ emissions. It operates five nuclear units, 31 hydroelectric power plants and two photovoltaic power plants.
The company’s commitment to producing electricity from low-carbon sources makes it a leader in sustainable energy generation in Central and Eastern Europe. The company has been included five times in the prestigious Europe’s Climate Leaders ranking, compiled since 2021 by The Financial Times and Statista.
Slovenské elektrárne, a.s., has two shareholders. The majority shareholder, with a 66% stake, is Slovak Power Holding B.V. (SPH), owned by the Czech energy group Energetický a průmyslový holding (EPH). The second shareholder is the Slovak Republic, which holds a 34% stake in Slovenské elektrárne.
