What role does nuclear play in the new paradigm?

Nuclear remains politically and strategically important in Bulgaria, consistently providing about 30–32% of total electricity generation through the Kozloduy Nuclear Power Plant. For decades, it has been regarded as a cornerstone of energy security and independence. However, in the emerging paradigm dominated by low-cost solar and wind, nuclear faces several challenges.

Inflexibility is a key issue. Kozloduy’s units were designed for baseload operation, not for frequent ramping up and down to balance variable renewables. This makes it harder for nuclear to adapt to a system where midday demand is increasingly met by solar PV – as demonstrated in April 2025, when solar alone covered up to 80% of national demand according to ESO. In such moments, nuclear output cannot easily be scaled back without efficiency and economic losses.

Second, cost competitiveness is eroding. The figure below shows that nuclear power plant construction costs have risen sharply over time, in contrast to the declining costs of renewables. In the 1970s and 1980s, nuclear plants could be built at costs below USD 2,000/kW. Today, however, new projects often exceed USD 5,000–6,000/kW, with some cases going even higher.

This escalation reflects several factors: stricter safety regulations after accidents such as Chernobyl and Fukushima, the increasing complexity of reactor designs, long construction timelines, and high financing risks. These cost pressures make nuclear far less competitive compared to solar PV and onshore wind, which are now built at below USD 1,000/kW.