The MARI Platform: How mFRR Balancing Energy Trades Across Europe

The MARI platform is the piece of European market infrastructure that turns national mFRR reserves into one shared, cross-border pool. For a BESS asset manager, understanding how it clears bids is not optional background reading. It is the difference between a bid that earns revenue and one that never activates.

This guide goes beyond the platform basics covered in our Frequency Restoration Reserve overview, focusing on how the mechanics translate into bidding strategy for BESS asset managers.

What Is the MARI Platform?

MARI stands for Manually Activated Reserves Initiative. It launched in October 2022, connecting five TSOs at first, under Article 20 of the EU’s Electricity Balancing Guideline.

The MARI platform exists to solve one problem. National mFRR markets used to clear in isolation. A shortage in one country and a surplus next door could not offset each other. MARI lets that offsetting happen automatically.

From National Markets to a Common Merit Order List

Every participating TSO submits its standard mFRR bids into a shared Common Merit Order List, or CMOL. The MARI platform rebuilds this list every 15 minutes, a period it calls a Market Time Unit.

An Activation Optimization Function then selects bids from the CMOL. Its first goal is maximizing total economic surplus. Only after that, it also tries to minimize how many cross-border exchanges the platform needs to meet demand.

How Bids Clear on the MARI Platform

Clearing on the MARI platform is not simply “lowest price wins.” Two separate conditions both have to hold.

First, the bid has to fall inside the accepted portion of the merit order. This applies for its direction and Market Time Unit specifically. Second, enough Cross Zonal Capacity has to exist on the transmission path between the bidder’s zone and the demand.

That second condition is easy to overlook. A BESS asset can offer the cheapest bid on the entire MARI platform. It can still miss clearing, simply because the interconnector between its zone and the TSO with the shortfall sits congested.

Direct vs. Scheduled Activation on the MARI Platform

The MARI platform runs two activation modes side by side. Direct activation is continuous. A pool of bids sits ready. The platform matches a TSO’s balancing need against that pool instantly, whenever it arises.

Scheduled activation, in contrast, works more like the older national mFRR process. It just runs coordinated across the shared platform now, instead of staying confined to one country. Both modes draw from the same underlying CMOL.

Marginal Pricing and Indivisible Bids

Every bid that clears on the MARI platform in a given direction earns the same marginal price. The most expensive accepted bid sets that price, not what each bidder originally offered. This pay-as-cleared structure rewards accurate cost estimation over aggressive underbidding.

Bids can also carry an indivisible tag. An indivisible bid clears entirely or not at all. For a BESS operator, a smaller, divisible bid size can sometimes clear more reliably than one large indivisible block, even at the same price.

MARI Platform Bidding Strategies for Asset Managers

Understanding the mechanics is the starting point. Turning that understanding into a bidding strategy is where the real economics live.

Balancing Markets Are Getting More Complex to Bid Into, Not Less

European balancing markets, including mFRR, are moving toward gate closures set closer to real-time delivery. Bid and price resolutions are shrinking too. That combination opens the market to more participants. It also makes correctly positioning a bid harder than it used to be.

An asset manager bidding on the MARI platform faces this trend directly. A bidding process built around slow, infrequent adjustments falls behind. Reviewing and adjusting bid levels closer to each Market Time Unit keeps pace with how the market has evolved, more than setting a static schedule days ahead ever could.

Treat Bidding and Dispatch as One Decision, Not Two

A common mistake: design a bid in isolation, then react to whatever activates. Research on value-stacking in adjacent European reserve markets, covering FCR alongside imbalance participation, points to a better approach instead. Shape the bid itself around the asset’s later dispatch flexibility, not after the fact. The same logic carries over to mFRR bidding on the MARI platform.

This matters most when a BESS stacks mFRR revenue from the MARI platform with other services. Think FCR and FRR, the products this platform sits alongside. A bid that looks optimal for mFRR in isolation can quietly eat into the state-of-charge headroom another service needs later the same day.

Consider the Cost of Capacity Withholding

Larger BESS portfolios face a different question entirely. Should the operator bid a smaller volume than what’s physically available? Doing so can influence the clearing price instead of simply accepting it. Broader research on storage bidder market power has derived formal bounds on this behavior, validated in simulations calibrated to the ISO New England market. It shows when capacity withholding still pays off, and when it turns self-defeating.

For most independent asset managers, this is more caution than strategy. A BESS large enough to move the clearing price also draws more regulatory scrutiny. Still, the underlying principle explains something real: very large storage fleets sometimes bid less aggressively than their full capacity would suggest, even outside the specific market that research examined.

Do Not Ignore Congestion Risk in Bid Placement

Cross Zonal Capacity gates every clearing decision on the MARI platform. Because of this, a BESS asset manager should treat interconnector congestion forecasts as seriously as price forecasts. A bid priced to win on the merit order alone can still miss clearing when the path to demand runs constrained.

Diversifying bid exposure across delivery windows helps too. Concentrating volume only in the most profitable hours raises the odds that one congestion event wipes out a day’s expected mFRR revenue.

MARI Platform vs. PICASSO

The MARI platform and PICASSO share the same underlying logic: a shared merit order and cross-border clearing. Each applies that logic to a different reserve product, with different activation timing.

FAQ

Further Reading

Frequency Restoration Reserve (FRR)

Frequency Containment Reserve (FCR)

Fast Frequency Response (FFR)

Rahul Jalthar CEO

Rahul Jalthar is a Shenzhen-based renewable energy professional and Battery Energy Storage Systems (BESS) expert. He is the founder of SunLith and has over 13 years of experience working with lithium batteries, ESS/BESS solutions, and renewable energy systems.

See Full Bio

Solar Energy Energy Storage