NEMOs and TSOs Advance Redesign of SDAC Full Decoupling Fallback Mechanism

The July 2026 MCCG Q&A reveals that NEMOs and TSOs (via Workstream 2 of the SDAC Fallback Improvements track) are actively developing a redesigned full-decoupling fallback solution for the Single Day-Ahead Coupling (SDAC). Key elements under consideration include replacing explicit shadow-auction (SA) capacity allocation with a centralized implicit process (IDCT), and shifting TSO nomination deadlines to provide more time for SDAC processes before triggering full decoupling. Alignment with NRAs and ACER on these options is ongoing, and NEMOs/TSOs confirmed that further public consultation with market participants is expected before any final decision is taken, following an earlier consultation on a continuous-trading fallback option that has already closed.

The fallback mechanism determines how cross-zonal capacity is allocated and how reference prices are set when the SDAC auction fails, directly affecting price reliability, cross-border capacity allocation quality, and TSO scheduling security. A shift from explicit shadow auctions to implicit centralized allocation would change how market participants submit and reconcile cross-zonal nominations, with implications for nomination quality, timing windows, and network security processes.

This event captures an early-to-mid stage design process affecting one of the SDAC's critical resilience mechanisms. The Q&A shows unresolved tension between TSOs (who favor implicit/centralized nomination for operational efficiency and fewer mismatches) and market participants (who question whether implicit clearing genuinely improves nomination representativeness, and who want clearer comparative information on capacity allocation, volume clearing, and price-setting options). The explicit reference to ongoing NRA/ACER alignment signals this is moving toward a regulatory determination, but no formal proposal or decision has yet been published; the process remains at the consultation/analysis stage with WS2 investigating deadline-shift interactions with full vs. partial decoupling triggers. Market design implications include potential changes to the SDAC reference pricing methodology (rejecting OTC-price alternative pending further assessment) and to cross-zonal nomination processes, both of which affect price formation integrity and operational security in fallback scenarios.

Not explicitly specified in source; process falls under the EU Day-Ahead Market Coupling (SDAC) governance and coordination framework overseen by NEMOs, TSOs, NRAs and ACER.

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