Large-Scale BESS Deployment Under REPowerEU: Eastern European Countries Entering the BESS Market
The Eastern Europe BESS market has become one of the most closely watched storage opportunities in the European Union. As REPowerEU and its companion packages push renewable integration and energy independence, countries that built their grids for baseload coal and gas are racing to add flexibility. This case study follows a Netherlands-based renewable developer weighing how to enter these markets while balancing speed, stability and risk across Poland, Romania, Bulgaria and Hungary.
From Energy Crisis to a Flexibility Imperative
Russia's 2022 invasion of Ukraine turned energy security into a European emergency. The EU responded with REPowerEU, designed to end reliance on Russian fossil fuels, diversify supply and accelerate renewable generation and flexibility. The rapid rise of wind and solar exposed a structural gap: renewables alone cannot guarantee reliability when the wind drops or clouds roll in. Battery energy storage systems fill that gap by storing surplus electricity and releasing it on demand, making renewables dispatchable. For Eastern Europe this flexibility is now a strategic necessity rather than a nice-to-have. Every Member State amended its Recovery and Resilience Plan with a REPowerEU chapter, allowing unspent facility loans to be redirected toward grid upgrades and storage. By 2025 the EU had installed about 13 GW of utility-scale storage, with 4.9 GW added in 2024, yet analyses suggest the bloc needs roughly 200 GW of non-fossil flexibility by 2030.
The EU Funding Stack That Starts the Market
A suite of complementary instruments underpins storage expansion. The Modernisation Fund, financed by Emissions Trading System revenues, supports lower-income Member States and had disbursed around 15.4 billion euros by the end of 2024, with a July 2025 call allocating 3.66 billion euros that explicitly includes grid flexibility and storage. Because grants can cover 70 to 100 percent of eligible costs, this fund is well suited to first-of-a-kind installations where market revenues remain thin. The Recovery and Resilience Facility has catalysed early projects: Romania relaunched a 278 million euro call targeting solar-plus-storage, Bulgaria announced a 1.9 GWh tender, and Poland began consultations on a large national storage scheme. The Innovation Fund and InvestEU, channelled through the European Investment Bank, lower financing costs for higher-risk markets. The Fit for 55 package raised the 2030 renewables target to at least 42.5 percent and strengthened the carbon market that funds these schemes.
Comparing the Four Markets and the Ambition Gap
The central problem is an ambition-versus-instruments gap. National Energy and Climate Plans set high renewable targets but often lack quantitative storage targets or detailed market designs. Poland leads on installed base, roughly 120 MW, and has a national storage scheme worth about 1.2 billion euros plus a capacity market that lets storage secure long-term revenue contracts, yet it still lacks a comprehensive flexibility roadmap. Romania is a regional first-mover with around 50 MW operational, an aggressive REPowerEU-backed pipeline and a 1.2 GW battery target for 2030 that gives a clear timeline. Bulgaria is the frontier, with minimal current deployment but a 2024 energy law reform and a large 1.9 GWh tender that signal a major opening for early positioning. Hungary is the policy front-runner, with a sizeable state-aid program and high price volatility that supports arbitrage value, but it carries meaningful execution and regulatory risk.
What It Means for Developers and the Region
For a developer with limited capital, the decision is how to allocate across markets with very different readiness, regulatory clarity and risk. Grants and de-risking instruments from bodies such as the European Investment Bank and development banks are essential to cover high upfront capital expenditure, and the capital stack typically blends project finance, equity and subsidy. The strategic question is whether early subsidy-dependent projects can transition to commercial sustainability, and on what timeline, before markets commoditise. Entering early can build local supply chains and market leadership, but complex and evolving regulation raises the risk. The case is a useful reference for anyone assessing utility-scale storage in emerging EU markets.
Key Takeaways
REPowerEU reframed storage as part of the reform and resilience agenda, unlocking redirected EU funds for Eastern European grids.
The Modernisation Fund can cover 70 to 100 percent of eligible costs, making it ideal for first-of-a-kind BESS projects.
Poland leads on installed capacity and offers a capacity market for long-term revenue, but lacks a full flexibility roadmap.
Romania is a first-mover with a funded pipeline and a clear 1.2 GW target for 2030.
Bulgaria's 1.9 GWh tender and Hungary's state-aid program open early positioning, though both carry regulatory and execution risk.
The core challenge is an ambition-versus-instruments gap: high renewable targets but limited operational frameworks for flexibility at scale.
Disclaimer: This case study was developed and presented by BatteryMBA participants as part of the Case Study Track. Views, analysis and recommendations are the authors' own. BatteryMBA does not take responsibility for the accuracy or completeness of the content and it should not be relied upon as investment, engineering or legal advice.
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