04What happens when supply runs tight?
Dunkelflaute: when the wind dies and the sun's gone
How often does Germany go days with almost no wind or sun, and what keeps the power on when it does?
A Dunkelflaute is a cold, dark, windless spell when wind and solar together all but stop. Wattlas counts one when combined renewable output stays below 10% of demand for at least 24 hours.
There have been 14 such spells on record since 2021, and one in the 12 months to 14 October 2026.
The worst on record ran 97 hours in 2022, with renewables covering as little as 4% of demand at its floor.
The worst low-renewable spell in the 12 months, hour by hour. Wind and solar (the thin top bands) fall to almost nothing. Coal, gas, biomass, hydro and imports cover demand, and the day-ahead price rises to a peak each evening.
Hours when wind and solar covered less than the threshold share of demand, by month. Single low hours happen all year, summer nights included. The sustained multi-day spells that strain the grid cluster in the dark half of the year.
The generation mix on a normal stretch and during the Dunkelflaute. Wind and solar fall from a large share to almost nothing; coal, gas and net imports rise to make up the rest.
The name is German for "dark doldrums". Through such a spell the grid leans on firm power (plants that run whenever asked: gas, nuclear, hydro) and imports, which is why a high-renewable system still needs firm capacity, storage or strong links to its neighbours.
Every sustained low-renewable spell in German data since 2021, longest first. The November and December 2024 events, when day-ahead prices rose toward €1 000/MWh, sit near the top.
Questions
What is a Dunkelflaute?
A cold, dark, windless spell when wind and solar together all but stop. Wattlas counts one when combined renewable output stays below 10% of demand for at least 24 hours.
How many Dunkelflaute events has Germany had?
14 on record since 2021; the worst ran 97 hours in 2022.
How these numbers are made: The Dunkelflaute spell detector.
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