Slovakia's national power utility Slovenské Elektrárne has announced the energy start-up of the 471 MW Mochovce 4 nuclear reactor in Slovakia, following approval from the country’s Nuclear Regulatory Authority (Slovenské elektrárne press release, 21/09/2026). Mochovce 4 uses a VVER-440/V213 reactor. Construction began in 1986 but stalled in 1992. At full output, the unit can cover around 13% of Slovakia’s electricity consumption, raising nuclear generation to the equivalent of 77.5% of national demand.
The regulator authorised the process after assessing the results of the unit’s physical start-up, inspecting the facility and reviewing the relevant documentation. The unit reached criticality and minimum controlled power in August 2026.
Reactor output is set to increase through several testing levels, with electricity entering the Slovak grid at 20% capacity. Tests are intended to verify the reactor, turbine, generator and safety systems under operating conditions. The final stage includes a 144-hour run at full capacity.
Slovakia has five operational nuclear reactors, which generate around half of its electricity. Alongside the Mochovce units, the country operates two reactors at Bohunice. The government is planning a new large-scale reactor at Bohunice and assessing the potential deployment of SMRs.
Interested in Power Plants?
Enerdata has developed a market research service to screen, monitor and analyse the development of power generation assets.
Power Plant Tracker offers an interactive database and a powerful search engine covering power plants worldwide – including both installed and planned capacities for renewables and fossil fuels.