One platform, different paths: How MARI implementation and use vary across European TSOs

Europe’s mFRR landscape differs across geographic lines. While Spanish and Portuguese TSOs exchange thousands of GWh through MARI, Central Western European participants remain largely inactive. As more TSOs are connecting, including TenneT Netherlands (today), MARI is becoming more relevant.

This article examines how different European TSOs have implemented MARI, covering the contrasting approaches in Germany, Belgium, and the Netherlands, and what the Baltic experience reveals about shallow market dynamics.

The MARI platform in brief

MARI (Manually Activated Reserves Initiative) is the European platform for the exchange of balancing energy from frequency restoration reserves with manual activation (mFRR). As a refresher, mFRR is manually activated balancing energy that TSOs use to correct large or prolonged system imbalances.

MARI is one of the pillars of the Electricity Balancing (EB) Regulation, designed to create a more integrated and efficient European balancing market. As such, it complements PICASSO, the corresponding platform for automatic frequency restoration reserves (aFRR). Together, they provide the foundation of cross-border balancing coordination in Europe.

Under MARI, two types of mFRR activations are standardized:

• Direct activation (DA) – launched within the Market Time Unit (MTU) or up to 10 minutes before it begins; typically short and highly reactive.
• Scheduled activation (SA) – triggered at least 10 minutes before the MTU start, lasting for the full period.

While MARI was conceived as a single, harmonized platform, each country’s legacy products, contracts, and operational realities have led to different implementation outcomes.

Who’s using MARI, and how much?

Operational data from a recent ENTSO-E workshop covering MARI shows striking variation in mFRR activation volumes.

From January to October 2025, Spain and Portugal account for the vast majority of MARI mFRR activations, each handling several thousand GWh of up and down energy. By comparison, Belgium, the Baltics, and Central Europe remain marginal users.

Thus, while the Iberian system exchanges balancing energy across its well-interconnected grid, other regions are still adapting their operational processes or joining progressively.

For a closer look at how these dynamics play out in practice, we zoom in on different countries, starting wth the second-largest group of users: the Baltics.

The Baltic experience

Since joining MARI in October 2024, the Baltic TSOs have been active users, dispatching more mFRR energy than larger Central European participants. Notably, balancing prices repeatedly hit ±10,000 €/MWh, driven primarily by MARI activations rather than aFRR (the Baltic countries joined PICASSO more recently, in spring 2025).

The underlying issue is market depth. The Baltic balancing markets were already relatively shallow before MARI, with limited flexible assets able to provide mFRR. The shift to MARI coincided with other significant changes: the introduction of the 15-minute market time unit for balancing bids, a revised mFRR standard product, and updated processes. This increases operational complexity for balancing service providers adapting to the new rules. Moreover, the formerly single Baltic balancing area was split into three control areas (Estonia, Latvia, and Lithuania). Together, these changes further thin the market in the short term and raise the risk of high marginal activation prices.

Direct activations tend to trigger extreme prices more often due to their erratic nature. A sudden 20-30 MW activation – modest in absolute terms but significant for small markets – can corner available supply and push marginal prices up. Even scheduled activations can produce sharp spikes when volumes exceed available capacity.

In this context, renewable asset owners are often on the losing side, exposed to high balancing costs. Battery energy storage systems (BESS) that can respond within seconds seem to benefit from volatility. One report suggested that for a 2-hour BESS, ancillary service revenues have exceeded €1 million per MW annually, with projections up to €3.6 million in 2025.

However, this is unlikely to last. As new storage projects come online, some as large as 200 MW, the market should deepen and margins normalize. Extreme profits are a symptom of early-stage scarcity rather than a sustainable business case.

MARI implementation in Western Europe: Three approaches

MARI implementation varies significantly across TSOs, and understanding these differences is important for short-term traders with European portfolios. Germany, Belgium, and the Netherlands offer an interesting contrast.

Germany: The early mover

Germany’s four TSOs were among the platform’s founders, together with ČEPS (Czechia), and the country’s existing mFRR framework effectively became the MARI standard. A large, liquid balancing market means price spikes are rare: capacity is deep enough to absorb major activations smoothly.

Belgium: Full harmonization

Elia, Belgium’s TSO, chose full harmonization by adopting the MARI-standard mFRR product. This move shortened activation lead times and brought national rules in line with European ones, but also sidelined some established assets. For instance, traditional pumped-hydro plants that once played a stabilizing role could no longer bid under the tighter readiness requirements.

The result: a cleaner technical alignment but temporarily reduced diversity in available resources.

The Netherlands: Parallel products

TenneT Netherlands is scheduled to connect to MARI on 2 December 2025. However, it will retain its local noodvermogen (emergency power) product as the primary balancing tool and will not procure the standard MARI mFRR product for its own balancing needs. Rather than replacing it, TenneT will allow Balancing Service Providers (BSPs) to offer the standard mFRR product so that other TSOs can access Dutch flexibility through the MARI platform.

This structure reflects a regulatory constraint: while TSOs can decide which reserve products (aFRR, mFRR, or mFRRda) they use to manage imbalances, the standardized mFRR product definition is set centrally by ENTSO-E and the MARI platform. TenneT therefore cannot adapt the product’s technical specifications to its own operational needs, which is why it maintains noodvermogen as a parallel product, better aligned with Dutch grid operations.

Further expansion

Although MARI is central to Europe’s balancing market design, in practice, it remains a niche mechanism in most countries. As we’ve seen, activations are minimal outside Iberia and the Baltics. That is unlikely to change significantly as more TSOs connect, with France joining in January 2026, Romania in April 2026, and Poland in July 2026.

For short-term power traders, it’s good to note that platform membership alone doesn’t determine exposure. Market depth and local implementation matter significantly. Understanding each TSO’s path is important to anticipating price behavior and opportunity spreads across Europe’s balancing landscape.

Want to discuss how these dynamics affect your portfolio strategy across different bidding zones? Let’s talk.