Nordic TSOs set 24 November 2026 for removal of indivisible-bid attribute in aFRR and mFRR capacity markets

The Nordic TSOs have confirmed a final implementation date of 24 November 2026 (applicable to operational date 25 November 2026) for removing the 'Indivisible Bids Allowed' attribute from bid submission in the Nordic aFRR and mFRR balancing capacity markets. From that date all bids are considered divisible by default, and the 'Minimum Quantity' bid attribute becomes mandatory for every bid; indivisibility must instead be expressed by setting Minimum Quantity equal to the offered quantity. The Implementation Guide for the Nordic balancing capacity market has been updated, and BSPs can test the new implementation in the normal test environment from 15 September 2026 across manual user-interface entry, file upload and ECP channels. The change was first announced by the Nordic TSOs in March 2026.

Bid divisibility rules determine how much of an offered volume a capacity auction can partially accept, directly affecting clearing outcomes, acceptance rates and the shape of the balancing capacity supply curve. Making divisibility the default while forcing an explicit Minimum Quantity on every bid makes the use of block-type indivisibility transparent and deliberate rather than a default switch, which should improve auction efficiency and reduce unnecessary rejection of partially usable volumes. Because the attribute change touches all bid submission channels, every BSP active in the Nordic aFRR and mFRR capacity markets must adapt internal bidding systems and file formats or risk rejected bids at go-live.

This is a bid-format design change rather than a product change, but bid granularity is a first-order determinant of price formation in capacity auctions: indivisible blocks create non-convexities that can force the auction to skip cheaper volume, while default divisibility with an explicit Minimum Quantity lets BSPs set the true minimum technical block size instead of an all-or-nothing flag. The likely effect is a smoother merit order and marginally better cost efficiency in aFRR and mFRR capacity procurement, with the residual non-convexity now sized explicitly by the participant. The requirement that Minimum Quantity be populated on every bid is the operational risk point — silent defaults in BSP bidding stacks could translate into unintended indivisibility or malformed bids, which is why the TSOs open a two-month-plus test window from 15 September 2026 and stress testing across UI, file upload and ECP paths. The long lead time from the March 2026 announcement to a November 2026 cutover, and the separation of the technical implementation date (24 November) from the first affected operational date (25 November), indicate a controlled cutover typical of Nordic Balancing Model deliverables. Watch for whether portfolios with genuinely lumpy assets (large thermal, hydro units with minimum load constraints) see changed acceptance patterns, and whether the more explicit minimum quantities alter observed capacity prices in tight hours.

Nordic Balancing Model implementation; Nordic aFRR/mFRR balancing capacity market implementation guide and bid submission rules

BSP testing of the new bid attribute implementation opens in the normal test environment · 15 Sept 2026

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