Southeast Europe's Renewable Boom Is Exposing a New Reality: Battery Storage Is No Longer Optional

Battery storage for renewable energy is no longer simply a way to optimise solar and wind projects. Across Southeast Europe, it is becoming essential for maintaining grid stability as renewable capacity continues to grow.

For much of the last decade, renewable energy expansion across Southeast Europe was driven by a relatively simple objective: adding as much solar and wind capacity as possible, as quickly as possible.

That phase is now ending.

At Balkan Battery Day 2026, a panel discussion explored how integrating battery storage with renewables is becoming one of the defining challenges for the region’s electricity systems. The conversation is no longer about whether renewable energy will dominate future power systems, but about how those systems can continue operating reliably as renewable penetration increases.

Moderated by Kostis Geropoulos, Co-founder and Director of Energy & Climate at NE Global, the panel brought together experts representing technology providers, renewable developers, legal advisers and energy companies:

• Athanasios Plainos, Key Accounts Sales Manager Greece & Cyprus, LONGi Solar
• Efstathios Sideris, Country Manager Greece, Econergy Group
• Horia Grigorescu, Managing Partner, Grigorescu Partners
• Răzvan Copoiu, Deputy CEO, ENEVO Group
• Tasos Mantzaras, Head of Energy Management and BESS Projects, Rokas Renewables

Although each speaker approached the discussion from a different perspective, the conclusion was remarkably consistent: battery storage is no longer an enhancement for renewable energy projects, it is becoming a prerequisite for their continued expansion.

Renewable Growth Is Creating New Grid Challenges

One of the strongest themes throughout the discussion was the recognition that the success of renewable energy has introduced new operational challenges for electricity networks.

As Athanasios Plainos (LONGi Solar) bluntly described it, solar developers have effectively “created the problem” by bringing large volumes of intermittent generation into systems that were never designed for this operating model.

Periods of abundant solar generation increasingly lead to curtailment, negative electricity prices and grid congestion. At other times, rapid drops in renewable output require significant balancing resources.

According to several panellists, battery storage is therefore becoming essential not only for improving project economics but also for maintaining the physical stability and reliability of electricity systems.

Co-Located Battery Storage Is Becoming the Preferred Model

Another recurring theme was the growing distinction between standalone battery projects and renewable projects developed together with storage.

While standalone batteries provide valuable balancing and ancillary services, Efstathios Sideris (Econergy Group) explained why hybrid renewable-plus-storage projects are increasingly becoming the preferred development model.

Co-located batteries allow renewable projects to:

• reduce curtailment exposure
• smooth generation output
• optimise grid connection capacity
• improve capture prices
• participate more flexibly across electricity markets

According to Sideris, recognising this shift early enabled Econergy Group to reposition several projects towards hybrid configurations before market conditions became more restrictive.

Rather than adding storage later, future renewable developments are increasingly expected to integrate battery systems from the very beginning.

Romania Is Moving Into a New Phase of Market Maturity

The discussion also highlighted how rapidly Southeast Europe’s renewable markets are evolving.

Răzvan Copoiu (ENEVO Group) argued that Romania has already moved beyond the “emerging market” stage and is now entering a period of industrial-scale deployment for both renewable energy and battery storage.

Several factors are supporting this transition:

• clearer storage legislation
• removal of double taxation
• improved access to financing
• earlier integration of storage into project planning
• stable investment conditions

At the same time, Copoiu noted that market maturity brings new challenges, as competition for grid access, financing and balancing opportunities becomes increasingly sophisticated.

Battery Storage Is Becoming Critical Energy Infrastructure

The role of batteries is also evolving beyond commercial optimisation.

Tasos Mantzaras (Rokas Renewables) explained that battery storage is increasingly expected to perform functions traditionally provided by conventional thermal generation, including:

• frequency response
• voltage regulation
• system balancing
• renewable smoothing
• grid resilience support

As coal and gas-fired power plants gradually retire, batteries are becoming part of the infrastructure needed to maintain system stability.

Several panellists referred to the discussions following the Iberian blackout as a reminder that flexibility and resilience are becoming central priorities for European electricity systems.

Battery storage is therefore no longer simply a trading asset, it is increasingly becoming critical energy infrastructure.

Long-Duration Storage Will Be the Next Challenge

While battery storage was widely recognised as essential, the panel also acknowledged its limitations.

Athanasios Plainos pointed out that lithium-ion batteries primarily address short-duration balancing challenges rather than seasonal mismatches between summer and winter renewable generation.

This introduces another important challenge for Europe’s energy transition: long-duration energy storage.

According to the discussion, future electricity systems are likely to require a broader portfolio of flexibility solutions, including:

• battery storage
• hydrogen production
• pumped hydro
• flexible demand
• expanded transmission infrastructure

Rather than competing technologies, these solutions are expected to complement one another, each addressing different operational needs across the electricity system.

Cross-Border Cooperation Will Become Increasingly Important

Another recurring theme throughout the discussion was the growing importance of regional integration.

As renewable penetration increases, electricity systems across Southeast Europe are becoming more interconnected. Flexibility in one country may increasingly contribute to balancing needs in another.

Several panellists highlighted stronger interconnections between Greece, Bulgaria, Romania and the Western Balkans as an important step towards improving both energy security and market efficiency.

The discussion also explored the prospect of stronger electricity flows towards Central Europe as industrial electrification accelerates and demand for clean electricity continues to grow.

The broader conclusion was that Southeast Europe has the potential to evolve into both a renewable energy hub and a flexibility hub for the wider European market.

The Next Phase of the Energy Transition Will Be Defined by Flexibility

Perhaps the clearest takeaway from the discussion was that Europe’s energy transition is entering a much more operationally demanding phase.

For years, success was measured by how quickly new renewable capacity could be deployed.

Today, attention is shifting towards the systems that make high shares of renewable generation possible.

The next phase depends on:

• system flexibility
• battery storage integration
• dynamic balancing
• cybersecurity
• regional coordination
• transmission expansion
• operational optimisation

The discussion at Balkan Battery Day 2026 made one conclusion clear: expanding renewable generation is no longer enough on its own. Future electricity systems will depend on the ability to integrate flexibility at every level of the grid.

Battery storage is no longer simply supporting renewable energy. It is becoming one of the foundations on which the next stage of the energy transition will be built.