ACER Plans Overhaul of Pan-European Intraday Power Auction After EPEX Spot System Failure
Europe's energy regulator is redesigning the IDA1 intraday auction mechanism after a technical breakdown forced its cancellation during the week of August 17.
Europe's energy regulatory agency ACER is preparing "major changes" to the continent's first pan-European intraday power auction after a technical failure forced the cancellation of IDA1 during the week of August 17 (2026-08-17), a spokeswoman told Montel. The breakdown exposed the fragility of an auction architecture meant to unify cross-border intraday power trading across the EU. EPEX Spot, which operates the mechanism, was named as the exchange involved.4
IDA1 was designed as the backbone of continuous intraday integration — a single clearing mechanism allowing generators, retailers and traders to balance positions across borders in near real time. When it fails, parties revert to bilateral trading or capacity bookings, reducing liquidity and widening spreads. ICE Endex TTF front-month gas rose 3.77% to €68.31/MWh by the close on August 24 (2026-08-24), while THE M+1 gained 3.67% to €68.93/MWh the same session, signalling that European energy markets remain tight enough heading into autumn that intraday infrastructure failures carry real cost.4
ACER has not disclosed the specific technical root cause, but the use of "major" by the spokeswoman signals the agency does not view this as a routine software patch. The scope of any redesign — whether it touches the matching algorithm, communication protocols between transmission system operators, or data validation layers — has not been specified publicly. No timeline for the overhaul has been given.4
This is not ACER's first complex infrastructure task in recent months. The agency is working toward a January 20 (2027-01-20) deadline on new frequency containment reserve rules for the continental Europe synchronous area, intended to reduce blackout risk, Montel reported. That parallel workload suggests ACER's technical and legal teams are carrying a heavy queue of infrastructure fixes simultaneously.3
EPEX Spot has been at the centre of European spot power reform before. In May 2026, EPEX Spot told Montel that the price floor for the pan-European day-ahead auction would be lowered by EUR 100/MWh from May 29 (2026-05-29), after prices during the week of May 11 (2026-05-11) hit the existing floor of EUR -500/MWh.2
That floor adjustment was triggered by a solar surge. Montel EnAppSys director Jean-Paul Harreman warned on Thursday (2026-05-21) that deeply negative prices could force a rule change around the bank holiday weekend, when forecast sunshine across Europe was expected to push generation well above demand.1 The willingness to shift price floors and now overhaul intraday auction mechanics points to a regulator and exchange still calibrating rules to market realities that emerged faster than the original architecture anticipated.2,1
For traders, the immediate concern is whether IDA1 will be suspended again before ACER's changes are implemented. European power intraday markets retain depth through continuous trading on EPEX Spot's own platform and through XBID, the cross-border intraday platform, so a prolonged IDA1 suspension would not eliminate intraday trading entirely. But IDA1 provides price discovery benefits that continuous bilateral markets cannot replicate: anonymity, simultaneous clearing, and a single price across borders.4
The market faces a sequencing problem. ACER sets the rules; EPEX Spot operates the system. Implementing architectural changes quickly enough to prevent further auction cancellations depends on a regulatory-technical coordination process that European markets have not tested at this pace before.4
TTF's near-4% gain on August 24 (2026-08-24) is a reminder that European gas costs remain elevated heading into the autumn demand ramp. Tight gas and power markets reduce tolerance for infrastructure disruption: a cleared intraday auction lowers balancing costs across the grid, and its absence pushes those costs onto transmission system operators and ultimately onto end users. How quickly ACER converts "major changes" into a functioning amended auction is the signal traders and system operators will be tracking through the coming months.4