When the Midday Trough Deepened and the Evening Ramp Took Over — Week 22, 2026

EUnix Market Intelligence identified Duck Curve and Flexibility Stress as the selected flexibility story for ISO Week 22, covering 25–31 May 2026.

The story received a priority score of 89.26, supported by 95.85% detection strength and 82.31% confidence, and was classified as Critical.

At story level, the strongest signal was a maximum duck depth of 55.3 GW, alongside a maximum evening ramp of 40.0 GW and 68 critical residual-ramp intervals. The supporting analytics were led almost equally by demand_response_opportunity at 93.10 and duck_curve at 93.07, followed by ramping at 77.55 and storage_utilization at 62.54.

The underlying system profile explains why the flexibility signal was so strong. Average electricity demand was 48.2 GW, while renewable generation averaged 25.9 GW, leaving average residual load of 22.3 GW. Renewable output became especially influential around the middle of the day, with the average residual-load profile falling below zero during the late-morning and midday period before rising sharply into the evening.

The detailed daily-profile visualisation reports a minimum residual load of -13.6 GW, with the typical daily trough occurring around 11:00. It also identifies Monday, 25 May as the deepest daily duck-curve profile at 46.8 GW and Thursday, 28 May as having the strongest daily evening recovery at 54.6 GW.

There is an important metric-definition difference within the supplied charts: the story-level summary reports maximum duck depth of 55.3 GW and maximum evening ramp of 40.0 GW, while the dedicated daily-profile charts show 46.8 GW for the deepest daily duck curve and 54.6 GW for the largest evening recovery. These should therefore be treated as related but differently calculated indicators rather than interchangeable values.

Week 22 illustrates the operational challenge created when renewable generation and demand follow fundamentally different intraday profiles.

Electricity demand remained comparatively stable through much of the daytime, but renewable generation increased rapidly through the morning and reached its highest levels around the middle of the day. Residual load therefore collapsed precisely when renewable availability was strongest.

The system then had to reverse direction.

As renewable output fell during the afternoon while electricity demand remained relatively elevated, residual load increased rapidly toward the evening. This creates the characteristic second half of the duck curve: the system moves from conditions of potential excess renewable electricity to a requirement for substantial upward flexibility within only a few hours.

The timing shown in the charts is particularly important.

Daily troughs occurred around 11:00 on average, while the most concentrated ramping stress appeared around 16:00. The flexibility challenge therefore contains two operational windows rather than one.

The first is the midday absorption problem: sufficient flexible demand, storage charging or other controllable consumption is required when residual load becomes very low or negative.

The second is the afternoon-to-evening recovery problem: flexible supply or demand reduction must become available as renewable contribution declines and residual load rises again.

This explains why both duck_curve and demand_response_opportunity received analytical scores above 93. Storage can absorb part of the low-residual-load period, while responsive demand can reduce system pressure during the subsequent recovery.

The supplied data also show that flexibility requirements cannot be understood from the deepest trough alone. Monday produced the deepest daily curve, but Thursday recorded the largest evening recovery. Different days therefore created different types of system stress.

That distinction matters operationally. A deep trough primarily indicates the need to absorb or shift energy. A steep upward ramp is predominantly a power and response-speed problem.

Week 22 contained both.

The supplied analysis does not calculate actual battery, demand-response or generation revenues, so no specific monetary return should be inferred from these charts. What it does show clearly is the emergence of well-separated intraday flexibility windows. Storage assets benefit operationally from precisely this type of pattern: low or negative residual load creates a natural charging window, while the later recovery creates conditions in which stored energy may become more valuable to the system. The 42 hours of strong storage opportunity show that attractive charging conditions were distributed across the reporting week rather than concentrated in a single isolated event. Demand response displayed an equally strong opportunity duration of 42 hours, but with a distinctly different timing profile. Its highest score occurred at 17:00 on Tuesday, compared with the storage peak at 09:00. This temporal separation is commercially significant. It means flexibility does not necessarily need to perform the same service throughout the day. Consumption can potentially be shifted toward the renewable-rich morning and midday period and away from the high-ramp afternoon and evening period. The dedicated opportunity chart makes this relationship particularly visible: storage scores generally increase during the daytime trough, while demand-response scores rise as residual load and upward ramps strengthen later in the day. The relatively modest storage_utilization investigation score of 62.54, compared with 93.10 for demand-response opportunity, also suggests that the week should not simply be interpreted as a battery-revenue story. The broader signal is a system flexibility requirement, with value potentially distributed across storage, responsive demand and fast-ramping generation.

The key question for subsequent weeks is whether the combination of deep midday troughs and strong evening recovery persists.

Several indicators from Week 22 provide useful reference points: the story-level 55.3 GW maximum duck-depth signal, daily duck depths averaging 39.8 GW, the -13.6 GW minimum residual load, 68 critical ramp intervals, and the concentration of ramping stress around 16:00.

The consistency of the daily profile is particularly important.

Every day displayed a recognisable midday depression followed by evening recovery, although the magnitude varied significantly. Continued repetition would indicate that flexibility requirements are becoming structurally embedded in the daily operating pattern rather than being driven by occasional extreme days.

The balance between the two sides of the curve should also be watched closely.

Deeper residual-load troughs would strengthen the need for storage charging and demand shifting, while faster afternoon recovery would increase the requirement for dispatchable generation, battery discharge and responsive demand.

The Week 22 charts suggest that these requirements can occur almost sequentially: absorb electricity during the middle of the day, then provide upward flexibility only a few hours later.

For Week 22, the market signal is therefore not simply that Germany experienced another duck curve. It is that the distance between the midday trough and the evening system requirement became large enough, frequent enough and fast enough to turn flexibility itself into the central market story.