On 18 December 2025, ACER received two proposals from all electricity transmission system operators (TSOs) to amend the implementation frameworks for PICASSO and MARI, the EU platforms for exchanging balancing energy from frequency restoration reserves.
With its Decisions 12/2026 and 13/2026, ACER approved both proposals.
What are these implementation frameworks about?
Established under the Electricity Balancing (EB) Regulation, the implementation frameworks harmonise how balancing service providers (BSPs) participate in electricity balancing markets across EU Member States.
These markets allow TSOs to manage unexpected differences between electricity supply and demand. PICASSO coordinates cross-border exchanges of automatically activated balancing energy, while MARI coordinates manually activated balancing energy. Together, they enable TSOs to access balancing resources across borders and maintain system stability.
What did ACER decide?
TSOs proposed further harmonising the BSP prequalification process, which ensures that power generation or demand units meet the technical and operational requirements to participate in the market and provide balancing services.
ACER approved the proposals, introducing some amendments:
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A structured harmonisation process to further align the terms and conditions for BSPs.
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More harmonised prequalification requirements, including for switching, re-prequalification, termination of prequalification and data exchange.
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More prequalification options, providing greater flexibility and enabling faster market access.
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Easier access for smaller market participants through a simplified prequalification process.
Some requirements will continue to be set at national level as TSOs gain experience with the harmonised process.
What’s next?
TSOs have six months to submit proposals to their national regulatory authorities to align national terms and conditions with the new requirements. Once approved, TSOs will have 24 months to implement the harmonised prequalification process.
