Slovakiaโs Mochovce-4 nuclear power plant has connected to the national electricity grid for the first time, marking a key milestone in commissioning the VVER-440 reactor unit. Slovenskรฉ Elektrรกrne, the plantโs owner, confirmed that the first of the unitโs two turbine generators was synchronised with the grid at 20:41 local time on October 15 and began delivering electricity.
The connection took place while the reactor was operating at 20% of its design power, according to the company. Mochovce-4 has an installed electrical capacity of 471 MW and is expected to produce approximately 3.5 TWh of electricity annually once fully operational. This would represent around 13% of Slovakiaโs current electricity consumption.
Commissioning Continues With Further Testing
The grid connection followed inspections and tests of generator protection systems, electrical circuits and equipment required to transmit electricity. Slovenskรฉ Elektrรกrne said the next steps involve synchronising the second turbine generator and conducting additional tests as reactor power increases.
The remaining commissioning programme will assess technological, control and safety systems at progressively higher power levels, including at nominal capacity. Slovakiaโs nuclear regulator continues to supervise the process to ensure the unit meets the necessary requirements before entering full commercial operation.
Construction History and Reactor Specifications
The Mochovce-4 reactor reached first criticality on August 6, 2026, after fuel loading was completed in June. The unit uses a VVER-440/V-213 pressurised water reactor design.
Construction of Mochovce-3 and Mochovce-4 began in 1987, but work was suspended in 1991 because of funding difficulties. Development resumed in 2008, eventually leading to the commissioning of the two units at different times. Mochovce-3 connected to the national grid in February 2023 and completed commissioning later that year.
Nuclear Power Maintains a Major Role in Slovakia
Slovakia operates five nuclear reactor units across two sites: three at Mochovce and two at Bohunice. According to data from the International Atomic Energy Agency, the countryโs nuclear fleet generated approximately 65% of its electricity in 2025.
The addition of the Mochovce-4 reactor is expected to strengthen Slovakiaโs domestic electricity generation capacity. Its projected annual output of 3.5 TWh would make a substantial contribution to national electricity supply once commissioning is complete and the unit reaches full operation.