I-SEM Daily Briefing — 11 May 2026

Price Profile #

Std dev €27.7/MWh · Median €125.84/MWh · Periods above €150: 12 of 48 (25%)

The working week restored the shape on day one. Overnight trough (03:00–04:30 at €112) → morning ramp (06:00 €129 → 07:30 €155, +€26 in 90 minutes) → midday softness (12:00–15:00 at €115–124) → evening build (17:30 €159 → 18:00 €180 → 21:00 €195). The double-peak structure is back.

The morning ramp is smaller than earlier in the week — May 5 added €85, May 6 added €80, today added €26. Wind held flat at 22–25% through the ramp window, so this is demand-driven rather than wind-driven: commercial and industrial load coming online, not a wind collapse.

The evening build is steep and sustained: €127 at 16:30 to €195 at 21:00, with the sharpest single move between 17:00 (€142) and 18:00 (€180) — €38 in one half-hour pair. Wind was falling through this window (24% → 18%), so supply and demand were compounding simultaneously.

Zero periods above €200. The day was expensive but not scarce. Mid-merit gas was sufficient in every period.

Price vs Wind #

Mean wind: 23.2% · Range: 17.4%–32.1%

Range 17.4%–32.1% — the narrowest of the run by a significant margin. Wind was low and stable all day: no cannibalisation story, no wind-driven trough, no capture price anomaly. Gas sets the clearing price in every period.

This is the thermal-marginal regime. With wind locked in a 15-point band and gas marginal across all 48 half-hours, price movements track demand directly: up with the morning, soft at midday, up with the evening. The wind line barely registers as a chart feature — it moves slightly but drives nothing. In the thermal-marginal regime, fuel cost flows straight to the clearing price across the whole day.

The contrast with the two preceding days is sharp. Saturday had wind ranging 39–67% with prices suppressed flat. Sunday had wind ranging 24–74% and a dramatic evening build. Today had wind ranging 17–32% and a conventional working-day shape. In each case, the wind chart is the explanation.

Week in Context #

A full week of data now in view. The chart should show the arc: Mon 4 elevated (€152), the midweek peak (Wed €185), the working-week decline (Thu–Fri), the weekend collapse (€111–113), and today’s recovery to €138. The Mon-to-Mon comparison is directly readable — today’s line should sit roughly €15 below May 4’s across all hours, with a notably softer morning ramp.

Price Duration Curve #

Periods above €150: 12 (25% of day) · Above €200: 0 (0% of day)

12 above €150 (25% of the day), 0 above €200. The curve has a clean top shoulder — the 17:30–22:30 evening peak block — sitting above a broad mid-section.

25% of the day above €150 puts today in the middle of the run: more expensive than the weekend, less than Wed–Thu. The absence of any €200+ periods is the telling number. The day was uniformly elevated but never tight; mid-merit gas was sufficient in every period. Compare to May 4 (bank holiday Monday), which had roughly 30 periods above €150 — a wind difference of 10 percentage points accounts for the gap.

Peak / Off-Peak Spread #

Peak avg (07:00–22:00): €146.79/MWh · Off-peak avg: €123.17/MWh · Spread: €23.62/MWh

Back to positive after two negative weekend days: peak €146.79, off-peak €123.17. The conventional weekday structure returns.

The spread is modest — a good working-day spread is €60–100+. The reason: the off-peak window is dragged up by sustained gas-marginal overnight (€112–125 from 00:00–05:30), while the peak window contains plenty of soft midday hours (€115–130 from 10:00–16:30) alongside the genuine evening peak.

Like May 5’s €20.93, today’s true arbitrage spread is €23.62, not the €83.39 headline range. The range is what the chart shows; the window-average spread is what the economics allow.

BESS Dispatch Signal #

Simulated 1MW/2MWh battery, one optimal DAM cycle. Gross before network charges and capacity costs.

€107 gross. Charged at 03:00 (€112), discharged at 20:00 (€195), capturing €83 of spread. The charge window returned overnight — the first time since Friday. With working-day demand back and wind at only 23%, the midday wasn’t cheap enough to displace the overnight trough. In three consecutive days: 13:30 (Saturday), 13:30 (Sunday), 03:00 (Monday). The optimiser didn’t change strategy; the grid changed market state.

Commentary #

The working week returned and immediately restored the conventional shape. Demand climbed 11% to 3,810 MW, wind dropped to 23.2%, and the result was the first classic working-day double-peak since Friday: overnight trough at 03:30 (€112), morning ramp to €155 at 07:30, evening peak at €195 at 21:00. Peak/off-peak spread came back to positive €23.62 after two negative weekend days. The structure is familiar; the level is lower than you might expect.

The Monday-to-Monday comparison is the sharpest single illustration of what wind does to price level in this market. May 4, bank holiday Monday: 13% wind, 3,633 MW demand, €152.58 mean. May 11, working Monday: 23.2% wind, 3,810 MW demand, €137.93 mean. A working day with 177 MW more demand cleared €15/MWh cheaper — because in the thermal-marginal regime, wind determines which plants set the clearing price. The gap between 13% and 23% wind is the gap between peakers and mid-merit gas holding the floor. May 4 paid a low-wind premium that higher working-day demand couldn’t close.

For storage, €107 gross — practically identical to Sunday’s €110 on a €26 higher mean. The captured spread was €83 today versus €79 yesterday; almost the same number. The dispatch swing is the structural signal: in three consecutive days the optimal charge window moved 13:30 → 13:30 → 03:00. The optimiser didn’t change strategy; the grid changed market state. A renewable-rich weekend is structurally long at midday; a thermal-marginal working week is structurally long overnight. A real BESS operator needs both in their book, and a forecast layer that picks between them.