mFRR (Manual Frequency Restoration Reserve)

mFRR is the manually activated frequency restoration reserve. The Transmission System Operator calls individual bids to release aFRR back to its operating range and to address sustained imbalances. Full delivery is required within 12.5 minutes of activation. mFRR is currently the largest balancing-capacity revenue stream for grid-scale BESS in Estonia.

mFRR is the manually activated frequency restoration reserve. The TSO's control-room operator picks individual bids from a merit-order list and dispatches them by phone or via API. mFRR releases aFRR back to its working range and takes over for sustained imbalances that aFRR cannot handle alone. Full delivery is required within 12.5 minutes of activation.

Activation pattern

mFRR is the slowest and least automated of the three operating reserves but also the most flexible product to bid into. Bids come in two flavours: scheduled (committed for a specific block of trading periods) and direct activation (available on call but not pre-committed). Estonian BSPs typically bid into both. Activation prices in Estonia are dominated by sustained system imbalances after wind forecast errors and large generator outages.

Why it matters most for Estonian batteries

mFRR capacity revenue is currently the single largest revenue line for grid-scale BESS in Estonia. The market is shallow enough that a 5–10 MW battery shifts the marginal price by a meaningful amount; 1–2C duration fits, since mFRR activations rarely run longer than two hours. Stacking — bidding the same MW into mFRR capacity and aFRR/FCR simultaneously and re-allocating where dispatched — is what separates a 12% project IRR from 22%.

MARI and the EU integration roadmap

MARI (Manually Activated Reserves Initiative) is the European platform that does for mFRR what PICASSO does for aFRR — pool activation across all Continental TSOs into a single merit order. (TERRE is a separate platform, for Replacement Reserves.) The three Baltic TSOs (Elering, AST, Litgrid) connected to MARI on 10 October 2024, joining the German TSOs and ČEPS who went live in 2022. Estonian mFRR activations now flow through MARI's pan-European merit order, expanding the pool of bids available to Elering's control room beyond the Baltic-only market.

Live data

Estonia mFRR up and down clearing prices, updated hourly: mFRR clearing price chart.

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What is mFRR in electricity balancing?

mFRR (manual Frequency Restoration Reserve) is the manually activated reserve product the TSO uses to release aFRR back to its operating range and address sustained imbalances. The TSO selects individual bids from a merit order; full delivery must be reached within 12.5 minutes of the activation order. It is the slowest of the three frequency reserves (FCR / aFRR / mFRR).

How fast does mFRR activate?

mFRR is required to deliver its full activated power within 12.5 minutes of the dispatch instruction under Article 25 of the EU Electricity Balancing Guideline. Bids can be activated for either Scheduled Activation (SA, at the start of the next 15-minute MTU) or Direct Activation (DA, intra-MTU for fast-evolving situations).

How does mFRR generate revenue for grid-scale batteries?

BSPs operating batteries earn two revenue streams: a capacity payment for being available in their reserved hour (procured via the Baltic BBCM market) and an energy payment when their bid is actually activated through the EU MARI platform. In Estonia 2024–2025, the asymmetric up-vs-down spread on MARI made mFRR the highest-yield BESS product.

What's the difference between mFRR and aFRR?

aFRR activates automatically via a closed-loop signal within roughly 5 minutes; mFRR is dispatched manually by the TSO and has 12.5 minutes to reach full delivery. aFRR runs on the EU PICASSO platform; mFRR runs on MARI. aFRR is the workhorse for routine balancing; mFRR handles larger or longer-duration deviations.

Who can offer mFRR in Estonia?

Any market participant certified by Elering as a Balance Service Provider (BSP) — covering the prequalification requirements for mFRR (technical capability, communication protocols, sub-minute metering integrated with the Datahub, financial standing). Aggregators may pool smaller assets into a single virtual unit to meet minimum-bid thresholds. Certification is per-product, separate from FCR and aFRR.