In 2025, nuclear power remains the most reliable source of baseload stability in South-East Europe. Solar and wind are changing the regional generation mix, while nuclear contributes to maintaining frequency and limiting volatility. It also supports export surpluses in key systems and helps protect national balances from fuel price shocks. Nuclear capacity is not being added everywhere, but where it exists it remains central to system operation in the current decade.
Bulgaria’s Kozloduy provides the largest nuclear baseload
Bulgaria is the region’s core nuclear operator through Kozloduy, which runs two 1,000 MW VVER units. The plant provides about 2,000 MW of dependable baseload. In 2025, Kozloduy typically produces between 14 and 16 TWh annually depending on maintenance schedules and operating regimes. Nuclear accounts for more than one-third of Bulgaria’s total power generation.
Nuclear output supports Bulgaria’s position as one of Europe’s largest net electricity exporters. Annual net exports have been around 10 to 12 TWh in recent years. Nuclear is described as structurally responsible for a stable export floor, while coal and renewables influence the incremental volume. The presence of nuclear also supports wholesale price stability and investor confidence through non-volatile supply.
Romania’s Cernavodă supplies firm generation with high capacity factors
Romania’s main nuclear contribution comes from Cernavodă, operating two CANDU 6 units with combined installed capacity of roughly 1,400 MW. In a normal year, the units generate 10 to 11 TWh. They provide 18 to 20 percent of Romania’s total electricity consumption. Cernavodă operates with capacity factors often above 85 to 90 percent.
The plant’s output is positioned as less variable than renewables that fluctuate daily and hydro that varies seasonally. Cernavodă supports Romania’s supply curve and reduces reliance on coal and gas. It also strengthens the ability to export during periods of high generation. Romania’s broader programme includes plans to complete Units 3 and 4 during the next decade, which would raise nuclear to beyond 30 percent of national supply.
Paks and Krško extend nuclear coverage across regional power flows
Paks in Hungary operates four units with combined capacity of roughly 2,000 MW. The plant produces about 15 to 16 TWh annually and covers around half of Hungary’s electricity needs. Nuclear reduces dependence on gas-fired generation and softens import exposure even though Hungary is not a permanent net exporter like Bulgaria. It also helps stabilise cross-border prices and supply flows used by Romania, Serbia and Croatia.
Paks II is planned to add two new nuclear units in the early 2030s. In Slovenia, nuclear stability is supported by Krško, a plant jointly owned with Croatia. Krško has capacity of around 700 MW and typically generates between 5 and 6 TWh per year. Production is effectively split between Slovenia and Croatia, delivering Croatia roughly 2.5 to 3 TWh annually.
Croatia’s share is described as a stable low-carbon baseload contribution that reduces import needs and supports price stability while balancing wind and solar variability. Slovenia benefits from reduced fossil generation requirements tied to Krško output. Policy discussions in Slovenia include extending Krško’s operational life to 2043, or potentially building a second unit. These options are linked to reducing long-term system risk and improving competitiveness.
Nuclear absence shapes reliance on coal, gas, hydro and imports
Civilian nuclear generation is not present in Serbia, Bosnia and Herzegovina, Montenegro, Albania or North Macedonia in 2025. Their power systems rely on combinations of lignite, gas, hydro and rising renewables. Without nuclear, baseload stability depends on coal or imports when domestic resources are insufficient. Imports introduce price risk, foreign-exchange exposure and structural sensitivity to neighbouring market behaviour.
The source describes different exposure patterns across countries: Serbia has historically relied on lignite and hydro; Bosnia and Herzegovina has hydro diversity alongside coal but remains exposed in dry or stress scenarios; Albania faces vulnerability when hydropower output falls due to rainfall variability. In each case, the lack of nuclear is associated with structural exposure to external markets and reliance on fossil flexibility or price-driven imports.
Total regional nuclear output exceeds 40 TWh per year in 2025
Combining existing nuclear generation across wider South-East Europe yields a collective figure well above 40 TWh annually in 2025. Bulgaria contributes around 15 TWh, Romania around 10 to 11 TWh, Hungary around 15 to 16 TWh, and Slovenia roughly 5 to 6 TWh. The combined output is described as firm, schedulable baseload energy rather than intermittent generation. The scale is compared with the annual electricity consumption of a country the size of Serbia.
Nuclear output is also linked to market effects through reduced short-run marginal pricing pressure from gas and coal units when baseload volumes are available. This dampens wholesale price volatility by limiting exposure to fuel spikes. It also supports export saldos by enabling reliable export volumes for Bulgaria and Romania even when renewable output fluctuates. The source further attributes improved carbon exposure to replacing fossil-based electricity on a per-TWh-basis under domestic or indirect carbon mechanisms such as CBAM.
Nuclear supports renewable integration while expansion plans continue
Nuclear is described as providing a firm base that allows solar and wind growth by shifting balancing needs toward flexible resources rather than carrying total system load. It cannot ramp like gas or hydro, but it supports system balance as variable generation expands. In Bulgaria, the combination of nuclear plus coal is cited as creating room for rising solar without risking supply security. In Romania, nuclear plus hydro is described as providing structural flexibility while gas and imports handle residual balancing needs.
Krško’s stable output is described as making it easier for Croatia and Slovenia to integrate wind and solar without creating reliability concerns tied to variability management. Investment activity across the region is characterised as consolidation alongside selective expansion rather than decline. Bulgaria is pursuing new nuclear development including planned Belene alongside Kozloduy expansion options.
Romania is advancing its two-unit expansion plan plus additional small modular reactor initiatives, positioning its programme beyond domestic use toward a regional technology role. Hungary is moving forward with Paks II, while Slovenia is debating its nuclear future within an energy security and cost competitiveness framework that includes operational-life extension discussions for Krško up to 2043. For systems without nuclear capability in 2025, policy focus shifts toward balancing approaches using gas capacity, large hydropower investments, storage, imports and tighter market integration.
The source describes these non-nuclear pathways as requiring higher CAPEX for flexibility infrastructure alongside higher OPEX exposure tied to imported energy costs. In South-East Europe’s current context, nuclear remains positioned as the stabilising anchor supporting export strength, wholesale price grounding, reduced carbon exposure and integration of rapidly expanding renewables through the period ahead into 2030.
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