Daily guide · PT · 2026-08-28

Negative-price watch Portugal: 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.

This week's floor in Portugal reached -2,1 EUR/MWh, recorded on 23 August at hour 12. That midday timing is unsurprising: it aligns with peak solar output, when supply routinely outpaces demand. The week logged 14 negative-price hours, alongside 49 hours priced below 10 EUR/MWh, indicating that soft pricing extended well beyond the outright negative periods.

For readers, the signal is one of persistent daytime weakness rather than a single extreme event. A shallow floor of -2,1 EUR/MWh suggests negativity was mild but recurrent, and the broader cluster below 10 EUR/MWh points to structural midday oversupply. The maximum modelled probability of negative prices over the next seven days sits at 0,05, so the forward risk remains contained.

The concrete takeaway: with 2.044 negative periods year-to-date, Portugal's midday value erosion is now a standing feature, not an anomaly. Load that can flex into the hour-12 window continues to capture the clearest advantage, while the low forward probability of 0,05 means the coming week is more likely to test the sub-10 band than to breach zero repeatedly.

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 PT stands.

-2.1

this week's floor (€/MWh), 2026-08-23 at 12:00 local

14 / 49

hours below €0 / below €10 this week

2,044

negative delivery periods in 2026 so far (PT)

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 PT over the next 7 days at 5%. That number updates daily via GET /v1/risk/negative/PT — 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": "PT", "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 PT tracker has the all-time records, monthly history and a CSV download — free to cite with attribution. For the systematic view (which hours, which seasons, how deep), the full 2015+ archive is one bulk export away.

Live PT 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-pt-2026-08-28".

The monthly European power roundup

Negative-price records, the biggest spreads, which zones were hardest to forecast — every number computed from our production data, on the 2nd of each month. No filler, unsubscribe anytime.