The Mochovce-4 nuclear power plant in Slovakia has been connected to the national electricity grid for the first time, marking a major milestone in the commissioning of the VVER-440 reactor unit.
Slovak owner Slovenské Elektrárne said the first of the unit’s two turbine generators was synchronised with the grid at 20:41 local time on 15 October and began supplying electricity.
A statement said the connection took place with the reactor operating at 20% of its design power.
Mochovce-4 has an installed electrical capacity of 471 MW. Once fully operational, it is expected to generate about 3.5 TWh of electricity annually, equivalent to approximately 13% of Slovakia’s current electricity consumption, Slovenské Elektrárne said.
The company said grid connection followed a series of inspections and tests of generator protection systems, electrical circuits and equipment needed to transmit electricity.
The next commissioning steps include synchronisation of the second turbine generator and further testing at progressively higher reactor power levels.
According to Slovenské Elektrárne, the tests will verify technological, control and safety systems up to nominal power. Commissioning remains under the supervision of Slovakia’s nuclear regulator.
Mochovce-4 reached first criticality on 6 August 2026, following the fuel loading in June.
The unit is a VVER-440/V-213 pressurised water reactor. Construction began in 1987 alongside Mochovce-3, but work was suspended in 1991 because of funding difficulties and resumed in 2008.
Mochovce-3 was connected to the grid in February 2023 and completed commissioning later that year.
Slovakia has five nuclear reactors units at two sites – three at Mochovce and two at Bohunice.
In 2025 they generated about 65% of the country’s electric power, according to data by the International Atomic Energy Agency.
