Market coupling has been one of the most ambitious and consequential reforms in European electricity markets. By linking national day-ahead markets through implicit capacity allocation, coupling aims to ensure that electricity flows from low-price to high-price zones, maximising welfare and reducing volatility. For South-Eastern Europe, market coupling has been both transformative and incomplete.
On paper, progress has been substantial. Day-ahead coupling now connects most SEE markets either directly or indirectly to the wider European system. Price formation in countries such as Serbia, Romania, Bulgaria, and Greece increasingly reflects regional conditions rather than purely domestic factors. Cross-border trade volumes have grown, and price convergence has improved during normal operating conditions.
Yet recent stress events reveal the limits of this integration. During periods of high demand, low renewable output, or network outages, price divergence re-emerges rapidly. Markets that appear integrated on average fragment under pressure. This raises a critical question: has market coupling delivered structural resilience, or has it merely redistributed volatility?
Quantitative evidence suggests a mixed answer. Under normal conditions, coupling has reduced average price differences between neighbouring SEE markets by 10–20 percent compared to pre-coupling periods. However, during stress events, price spreads can widen dramatically, sometimes exceeding €100/MWh for extended hours. These divergences coincide with reduced cross-zonal capacity availability, whether due to physical constraints, maintenance, or conservative operational margins.
This pattern indicates that coupling effectiveness is conditional. It works when capacity is available and rules are aligned. It falters when institutional and technical constraints intervene. In that sense, SEE market coupling remains a structural half-measure: sufficient to improve efficiency in calm periods, insufficient to guarantee stability during storms.
The limitation is not inherent to coupling itself, but to its scope. Day-ahead coupling alone cannot address real-time volatility in a system dominated by variable renewables. Intraday markets and balancing platforms are essential complements. In SEE, intraday liquidity remains uneven, and balancing integration is still developing. Without deep intraday and balancing coupling, day-ahead price convergence can unravel within hours.
The consequences were visible during summer 2024. Despite formal coupling, extreme evening price spikes occurred in parts of SEE, driven by post-sunset demand peaks and constrained imports. Analysis showed that fuller utilisation of cross-zonal capacity could have mitigated many of these events, highlighting that coupling without capacity availability is fragile.
Market coupling also interacts with national policy choices. Capacity mechanisms, network tariffs, and renewable support schemes vary widely across SEE countries. These differences distort price signals and complicate cross-border flows. For example, if one market subsidises availability while another relies purely on energy pricing, dispatch incentives diverge. Coupling transmits prices, but not necessarily investment signals.
Institutional fragmentation further weakens integration. Some SEE countries are EU members bound by full market design obligations; others operate under the Energy Community framework with transitional arrangements. While alignment has progressed, differences remain in implementation speed, enforcement, and regulatory culture. These gaps matter most during stress, when coordinated action is required.
From a welfare perspective, the gains from deeper coupling are substantial. Studies estimate that balancing market integration alone has delivered over €1.6 billion in welfare gains across Europe. For SEE, similar proportional gains are available if integration extends beyond day-ahead trading into balancing and reserve sharing. Such integration would allow flexibility to flow where it is needed most, reducing both price volatility and reserve costs.
The political challenge is governance. Deeper coupling requires trust among transmission system operators, harmonisation of grid codes, and willingness to share control. In regions with strong national narratives around energy sovereignty, this is not trivial. However, the alternative is persistent exposure to volatility that undermines sovereignty in a different way: through price shocks and import dependence during crises.
Looking forward, the question is not whether SEE should pursue deeper coupling, but how fast and how coherently. Incremental progress risks locking the region into a pattern where integration works in theory but fails in practice during critical moments. Accelerated alignment of capacity calculation, outage planning, intraday markets, and balancing platforms offers a path toward genuine resilience.
Market coupling in SEE has already changed how electricity is traded and priced. The next phase will determine whether it becomes a true stabiliser or remains a partial solution. The evidence suggests that without completing the integration stack, coupling alone cannot deliver the stability that high-renewable, high-volatility systems require.
By virtu.energy
