When Schedules and Physical Flows Pulled Apart — Week 21, 2026

EUnix Market Intelligence identified Schedule and Physical Flow Mismatch as the selected market story for ISO Week 21, covering 18–24 May 2026.

The story received a priority score of 82.49, supported by 88.44% detection strength and 68.37% confidence.

The defining event was a maximum physical–schedule deviation of approximately 27,094.6 MW, recorded on Friday, 22 May at 04:15 UTC. At that point, the physical position was dramatically below the corresponding scheduled position.

The detailed charts report an average absolute interval deviation of approximately 11.6 GW, with an RMSE of 13.5 GW. Operational alignment was assessed at 0.0%, classified as poor, because all 672 monitored intervals exceeded the 100 MW deviation threshold.

The overall signed deviation was approximately -6.9 GW, indicating that physical net positions tended to sit below scheduled positions over the week.

The supporting analytics were led by schedule_deviation at 89.48, followed by scheduled_net_position at 63.63 and border_balancing at 30.87.

Week 21 is notable not merely because scheduled and physical cross-border positions differed, but because the divergence was large, persistent and directionally systematic.

A schedule represents the commercial position anticipated through market processes. Physical flows, however, reflect what ultimately moves through the interconnected electricity system subject to network physics, system conditions and cross-border interactions.

Some difference between these quantities is therefore expected.

What makes Week 21 unusual in the supplied data is the scale.

An average absolute mismatch of around 11.6 GW is already substantial. A peak deviation above 27 GW, coupled with a 0.0% operational-alignment assessment, indicates that the scheduled and realised positions behaved as distinctly different signals during the week.

The -0.994 correlation is especially important. Rather than simply showing noisy deviations around a common trajectory, the chart indicates that scheduled and physical positions frequently moved in opposing directions.

This is also visible in the main net-position chart. When the scheduled series moves strongly positive, the physical series is frequently negative, and vice versa. The mismatch therefore reflects more than occasional timing errors or small forecasting differences.

However, the balancing-gap analysis introduces an important qualification.

The relationship between schedule deviation and the measured border-balancing gap is weak, with r = -0.34 and R² = 0.12. Large schedule deviations therefore did not consistently correspond to proportionally large balancing gaps according to the supplied metric.

That makes it inappropriate to interpret every schedule–physical difference as direct balancing-system stress.

Instead, the Week 21 story is fundamentally about operational divergence between commercial schedules and realised cross-border system positioning.

Large schedule–physical deviations create economically relevant conditions because market participants, system operators and flexible assets ultimately respond to the physical system, even when commercial positions were established earlier through scheduled market processes. Week 21 contained several long-duration and high-magnitude mismatch periods. The eight identified events accumulated approximately 647.7 GWh of absolute mismatch energy, and the three Extreme events accounted for the majority of that event exposure. This persistence matters commercially. Short deviations may be handled largely as transient operational effects. Multi-hour divergences, particularly those exceeding 20 GW, can potentially affect intraday adjustment requirements, balancing exposure, congestion management and the value of flexible resources. The largest persistent event alone contributed approximately 162.1 GWh of mismatch energy over 7 hours 30 minutes. Such conditions increase the value of accurate intraday forecasting and the ability to revise positions closer to real time. Storage, demand response and fast-ramping generation may also become more valuable where physical conditions diverge materially from earlier market expectations, although the supplied data do not quantify revenues from those assets directly. The relatively low border_balancing analytical score of 30.87 also matters. It suggests that the primary economic story this week is not simply unusually large balancing-gap monetisation. The stronger signal is the size and persistence of the schedule-to-physical divergence itself. For market participants, the core commercial lesson is therefore one of forecast quality, position reconciliation and intraday adaptability.

The most important question is whether Week 21 represents a temporary anomaly or the beginning of a recurring pattern of large schedule–physical divergence.

Several indicators would be particularly important to monitor in subsequent weeks: average absolute deviation, maximum deviation, directional bias, duration of persistent mismatch events, operational alignment and the relationship between system-level deviations and individual border contributions.

The directional pattern also deserves attention.

With approximately 73.2% of hourly cells showing negative deviation, Week 21 was clearly asymmetric. A continuation of that bias would suggest something structurally different from randomly distributed forecasting error.

France should also remain under observation because it was identified as the largest contributing border, with approximately 3.27 GW average absolute mismatch.

At the same time, the weak connection between schedule deviation and border-balancing gap should not be ignored. If future weeks continue to show large schedule mismatches without correspondingly strong balancing-gap relationships, the evidence would increasingly support the interpretation that commercial schedules and physical cross-border positions are measuring fundamentally different system dynamics rather than one simply being an inaccurate version of the other.

For Week 21, the market signal is clear: the schedule said one thing, while the physical system repeatedly did something very different.