Curtailment has evolved into a critical financial factor for renewable energy projects across South-East Europe, where the anticipated growth of renewable capacity is projected to reach between 20–25 GW by 2030. The existing transmission infrastructure, primarily based on legacy 400 kV corridors, has failed to keep pace with this expansion. Consequently, the region faces not only congestion issues but also significant revenue erosion for renewable energy projects, which is increasingly factored into financing arrangements and power purchase agreements (PPAs).
The geographical distribution of curtailment reveals stark contrasts within the region. In northern areas, especially those linked to Central Europe via Hungary and western Romania, curtailment levels remain relatively low. For instance, around the Subotica–Sandorfalva corridor, transfer capacity can reach between 1,200–1,500 MW, with actual transfer capability (ATC) typically hovering between 600–1,000 MW. Here, curtailment is reported at under 3–5%, and solar capture prices remain close to baseload benchmarks.
The situation shifts dramatically in central regions such as Kragujevac, Kraljevo, and the Morava corridor, where ongoing investments of approximately €200–300 million aim to alleviate congestion during peak solar generation periods. Forecasts indicate that curtailment levels in these areas can range from 5–15%. For a typical 100 MW solar facility generating 150 GWh annually, this could result in lost production between 7–20 GWh, translating to annual revenue losses of about €0.6–2.0 million.
In Bosnia and Herzegovina, similar trends are observed around the nodes of Tuzla and Sarajevo, where outdated infrastructure restricts export capabilities. New solar developments are facing projected curtailment rates of 10–20%, particularly during summer months when hydroelectric output peaks but local demand fails to keep up.
The most severe curtailment challenges are found in southern Serbia, North Macedonia, and Albania. Here, limited northbound transfer capacity—often restricted to between 400–700 MW ATC—intersects with rapidly expanding solar installations. Financial models for projects in these regions now incorporate curtailment levels ranging from 20–30%. For a standard 100 MW plant, this could mean an annual loss of output between 30–45 GWh, equating to foregone revenues of approximately €2.5–4.5 million.
The Romanian energy landscape presents a more complex scenario. While northern and western nodes benefit from robust interconnections, the Dobrogea region, which hosts the country’s largest wind farms exceeding 3 GW of installed capacity, grapples with transmission constraints that lead to periodic curtailments estimated at around 5–10%. These figures can spike above 15% during conditions of high wind generation paired with low demand.
Bulgaria’s grid also reflects disparities; while northern nodes operate stably in alignment with Romania’s network, southern corridors towards Greece face volatility due to solar saturation and fluctuating cross-border flows. During peak solar generation periods, southern Bulgaria experiences curtailments as high as 15–25%.
The distinct case of Montenegro arises from its connection via a 600 MW HVDC link to Italy, allowing for surplus generation export. However, internal grid limitations coupled with low domestic demand can still lead to localized curtailment risks as new renewable projects come online without parallel network reinforcements.
Curtailment impacts vary by technology; solar power is particularly susceptible due to its concentrated generation profile during midday hours when demand is typically lower. Wind energy experiences comparatively lower levels of curtailment—averaging between 3–8%in less congested areas and reaching up to10–15%in saturated zones.
The financial ramifications of curtailment extend beyond mere production losses; they significantly influence price formation processes and amplify capture discounts. The interplay between curtailed solar output and prevailing market prices often results in lower realized revenues for remaining generation during constrained periods.
Lenders are increasingly adjusting their debt sizing methodologies based on revised production scenarios that account for potential curtailments rather than relying solely on theoretical generation estimates. This shift necessitates reevaluating cash flow projections for debt servicing purposes.
A growing emphasis on mitigation strategies is evident in project planning; energy storage solutions are being prioritized as a means to manage excess generation effectively. Deploying batteries alongside renewable installations can significantly reduce effective curtailment rates while enhancing overall revenue potential.
The evolving landscape also influences PPA structures as industrial consumers become more amenable to accepting variable delivery profiles in exchange for better pricing terms. This trend reflects a broader recognition among stakeholders about integrating flexibility into contracts based on actual delivered energy rather than theoretical outputs.
A long-term solution lies within grid investments aimed at enhancing transfer capacities across key corridors such as the proposed Trans-Balkan Corridor and Bulgaria-Greece reinforcements, which could potentially increase capacity by up to40%and mitigate some current challenges.
The rise of data analytics tools is becoming essential for managing curtailment risks effectively. Platforms providing detailed insights into congestion patterns and price dynamics enable stakeholders to develop more accurate modeling scenarios that inform both project development and financing decisions.
Curtailment has transitioned from being an incidental operational issue into a fundamental aspect impacting investment strategies throughout South-East Europe’s energy sector. As developers increasingly prioritize sites with improved grid access over locations with superior resource quality alone, understanding the implications of these dynamics will be crucial for all market participants navigating this complex environment.
