Daily guide · ES · 2026-09-12

Negative-price watch Spain: this week's floor, and what's ahead

All numbers computed from the week's published auction results at publication and frozen — this article is an honest snapshot, not a page that rewrites itself. Reproduce via the API.

Spain did not print a single negative hour this week. The weekly floor landed at 0 EUR/MWh on 6 September at hour 12, exactly where you would expect it: the solar midday window. The floor held at zero rather than dipping below it, but the pressure around that level is clear, with 17 hours settling below 10 EUR/MWh over the week.

The signal for readers is that the market is running close to the negative-price threshold without crossing it. Our model puts the maximum probability of a negative period over the next seven days at 0,93, so the risk is priced as near-certain to materialise at some point in the window. This week's zero prints should be read as a floor being tested, not a stable equilibrium.

The concrete takeaway: treat the midday hours as the exposure point. With 2.649 negative periods logged year-to-date and 17 sub-10 EUR/MWh hours this week alone, the structural downward pressure is intact. Position for negative prints in the solar peak rather than assuming zero remains the floor.

When wind and solar produce more than a zone can consume or export, the day-ahead auction clears below zero — producers literally pay consumers to take power. Negative prices went from curiosity to structural feature across Europe, and for anyone with flexible load or storage they're the most interesting hours of the year. Here's where ES stands.

this week's floor (€/MWh), 2026-09-06 at 12:00 local

0 / 17

hours below €0 / below €10 this week

2,649

negative delivery periods in 2026 so far (ES)

The forward view

Our negative-price risk model (Brier-scored daily against climatology — record on /accuracy) currently puts the peak probability of a sub-zero period in ES over the next 7 days at 93%. That number updates daily via GET /v1/risk/negative/ES — a 14-day calendar of per-15-minute probabilities.

Never miss one again

The useful pattern isn't watching a dashboard — it's a webhook that fires when tomorrow's auction clears negative anywhere in your zone:

curl -X POST -H "Authorization: Bearer YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"event": "negative_prices", "zone": "ES", "url": "https://your-app/hook"}' \
  https://voltcast.com/api/v1/webhooks

It delivers seconds after the 13:00 CET publication, HMAC-signed. Journalists and analysts: the live ES tracker has the all-time records, monthly history and a CSV download — free to cite with attribution. Home+ can download its entitled interval prices and forward risk directly to Excel from the API; the full 2015+ archive remains a Pro+ bulk export.

Live ES prices → All daily guides → Start with Home →

Method & citation. Prices are hourly means of published day-ahead auction results (native 15-minute periods averaged; ENTSO-E/SMARD, attributed). Wholesale-price component only — grid fees and taxes come on top and vary by supplier. Cite as "Voltcast Research, voltcast.com/guides/negative-watch-es-2026-09-12".

Next issue 2 Oct

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✓ Negative hours and the cheapest zones
✓ The month's widest day-ahead spreads
✓ Forecastability ranking — where we missed

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