In South-East Europe, Battery Energy Storage Systems (BESS) are emerging as a critical component of the electricity grid, bridging the gap between generation and transmission. As renewable energy sources expand and grid congestion increases, the role of battery storage is evolving from a supplementary technology to a fundamental layer of the power infrastructure. The region is poised to deploy between 3–5 GW of storage capacity by 2030, with Greece alone planning to add over 1 GW in upcoming tenders.
The economic viability of BESS in this region is heavily influenced by market price structures. In countries like Greece, Romania, Bulgaria, and Hungary, intraday price spreads have widened significantly. For instance, in Greece, the price difference between midday lows and evening peaks can reach €60–100/MWh, with extreme fluctuations exceeding €120/MWh. Bulgaria and Romania experience narrower yet substantial spreads, typically ranging from €30–70/MWh, particularly during high renewable output or limited interconnection periods.
These price dynamics create a revenue framework for battery systems. Current utility-scale installations are generally designed with a power capacity of 50–100 MW and a duration of 2–4 hours, translating to a storage volume of 100–400 MWh. With capital expenditure (CAPEX) costs estimated between €400–600/kWh, total project costs for a 100 MWh system can range from €40 million to €160–240 million for larger installations. Additional costs related to balance-of-plant and grid connections can elevate total expenses to between €50 million and €280 million.
The primary revenue stream for these systems comes from energy arbitrage—purchasing electricity during low-price periods and selling during peak demand times. For example, a 200 MWh system in Greece cycling approximately 250–300 times annually could generate gross arbitrage revenues of around €15–30 million per year. In Bulgaria and Romania, similar systems might yield between €10–20 million annually, depending on market conditions.
A secondary revenue source is derived from ancillary services such as frequency containment reserve (FCR) and automatic frequency restoration reserve (aFRR). These services are becoming increasingly accessible as regulatory frameworks evolve, contributing an additional €20–40/MW/year, which could amount to roughly €1–4 million annually for mid-sized systems. Although these ancillary revenues are smaller than those from arbitrage, they provide enhanced revenue stability.
The interplay of these revenue streams results in equity returns aligning with infrastructure investment benchmarks. Battery projects across South-East Europe aim for equity internal rates of return (IRRs) between 12–16%, with potential upside reaching up to 18–20% in high-volatility markets like Greece. Debt financing options are becoming more accessible, with leverage ratios of 50–65% and terms extending from 8 to 12 years.
The integration of storage with renewable generation further enhances these returns. Hybrid projects that combine solar or wind generation with co-located batteries are central to development strategies in Serbia, Bulgaria, and Greece. A typical configuration might involve a 100 MW solar facility paired with a 200 MWh battery, potentially increasing realized prices by approximately €8–20/MWh. This synergy can lead to additional annual revenues ranging from €10–25 million, boosting project IRRs by about 2–4 percentage points.
In Serbia, early-stage hybrid projects are being developed in areas facing curtailment risks exceeding 10–15%. Collaborations with trading partners such as GEN-I, MET Group, and EFT focus on optimizing asset performance while managing both price and volume risks. These initiatives are particularly evident around nodes like Kragujevac and Niš, where solar clustering presents both challenges and opportunities.
The Greek market stands out as the most advanced in terms of storage deployment. Government-backed initiatives have spurred rapid growth, particularly around regions characterized by high volatility such as Thessaly, Central Greece, and the Peloponnese. The integration of storage with Greece’s substantial solar fleet—estimated at around 7–8 GW—is reshaping intraday pricing patterns by alleviating extreme midday price drops while maintaining viable arbitrage opportunities.
Romania’s trajectory mirrors that of Greece, driven by renewable energy expansion alongside grid constraints in areas like Dobrogea.
Bulgaria’s storage pipeline is smaller but expanding, especially in southern regions where interactions with Greek pricing dynamics present strong arbitrage potential.
The role of trading firms is also evolving within this ecosystem. Companies such as Axpo, MET Group, and PPC Trading not only facilitate market access but also serve as optimization partners leveraging advanced algorithms and real-time data analytics to maximize battery revenues. The value derived from storage hinges on precise timing and responsiveness to market signals.
BESS also plays a significant role in shaping transmission dynamics by absorbing excess generation during peak renewable production periods and releasing it during high demand phases. This capability alleviates stress on interconnections while enhancing the utilization of existing infrastructure, impacting congestion pricing and flow patterns significantly.
The growth of storage capacity introduces new complexities into the market landscape. As competition for arbitrage opportunities intensifies, there are indications that extreme price spreads may begin to stabilize due to the smoothing effects of storage technologies. This shift underscores the growing importance of ancillary services and multi-market participation as alternative revenue sources.
The regulatory framework remains crucial for sustaining investment in this sector. Clear guidelines regarding market participation, access to ancillary services, and treatment within grid tariffs are essential for fostering growth. While countries like Greece and Romania have made strides in this area, others such as Serbia and North Macedonia continue to develop comprehensive frameworks that fully recognize storage’s value.
The emergence of BESS signifies a new asset class within South-East Europe’s energy landscape. Unlike traditional generation assets tied closely to production metrics, storage derives its value from flexibility and timing considerations—creating a distinct risk profile more aligned with market dynamics than resource variability.
The strategic positioning of storage assets is vital; those located near high-volatility nodes or key interconnections can capture greater value compared to those situated in more stable areas that may depend heavily on ancillary service revenues. The integration capabilities across generation, transmission, and trading strategies will be pivotal in determining how effectively projects achieve their financial targets.
The ongoing deployment of BESS across South-East Europe is fundamentally altering both the physical infrastructure and financial architecture of the power system. This evolution facilitates increased renewable energy penetration while mitigating curtailment issues and generating new value forms. However, it also introduces layers of complexity demanding sophisticated operational expertise as the region transitions toward a more interconnected energy landscape.
