MONTHLY NEGATIVE HOURS
ℹ Data Quality  Multi-source pipeline · All six markets covered · Whole-hour counting (mean price < 0) applied uniformly across all countries and resolutions.

Negative price hours are assembled from two authoritative sources to maximise completeness and accuracy across all six markets:
  ‣ Spain & Portugal: OMIE (Iberian market operator) — primary source for both countries. Provides quarter-hourly (PT15M) settlement prices from October 2025 onwards; hourly (PT60M) prices for earlier periods.
  ‣ Belgium, France, Netherlands & Germany: ENTSO-E Transparency Platform A44 (EPEX SPOT clearing prices, PT60M).

A negative price hour is counted as 1 hour whenever the mean Day-Ahead clearing price across all settlement intervals within that clock hour is strictly below zero (EUR/MWh). For PT60M markets (one price per hour) this is identical to a direct comparison; for PT15M markets (four 15-minute prices per hour) the arithmetic mean of the four slots must be negative for the hour to count. This uniform whole-hour methodology ensures full comparability across all six countries and across the pre/post October 2025 period for Spain and Portugal, and is consistent with how industry references (Kpler, REE/ESIOS, SMARD) report negative price statistics.

Historical data freeze: Once a calendar month closes, its negative hour count is locked and not revised even if the source APIs later publish corrections to historical prices. Only the most recently completed month is re-derived on each monthly pipeline run. This guarantees that historical counts are stable and reproducible.

DST spring-forward transitions naturally yield 23 hours on one Sunday each March; these are not data gaps.  ·  Not investment or trading advice.  ·  Data Sources

ANNUAL PERFORMANCE
DAILY BREAKDOWN
Distribution of negative price hours across each day of the year. Each cell indicates the total number of negative hours recorded on that specific date.
INTRADAY PATTERN
Observation of which hours of the day are most prone to negative prices. Each cell represents the total number of negative hours for that specific hour across all months of the selected year.
WEEKLY PATTERN
Analysis of negative price variation by day of the week and hour. Each cell shows the cumulative number of negative hours for a specific weekday and hour combination during the selected period.
PRICE DISPERSION
Country:
Year:
Each point is one hour with a negative Day-Ahead clearing price. Colour indicates time of day: solar hours (08–18h), night (22–06h), or morning/evening (07h–08h and 19–21h).
CUMULATIVE NEGATIVE PRICE
Country:
Year:
Metric:
NEGATIVE HOURS VS INTRADAY SPREAD
Year:
Each point is one country. X: total negative-price hours in the selected period. Y: average daily spread on those days, modelled as a 2-hour battery dispatching optimally once per day (mean of the 2 peak-price hours minus mean of the 2 lowest-price hours, €/MWh).
NEGATIVE PRICE EVENTS
Total Events
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Longest Event
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Most Negative Hour
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Date ↕ Start ↕ Duration ↕ Avg (€/MWh) ↕ Min (€/MWh) ↕ Intensity (€·h) ↕
An event is a consecutive block of negative-price hours. Intensity (€·h) is the sum of absolute prices across all hours of the event, a rough proxy for storage charging revenue.

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