Spotlight: Dunkelflaute events as potential stress tests
Temporary periods with reduced wind and solar PV generation may put additional strain on the power system, especially if they occur during periods of high electricity demand, such as during colder winter seasons with increased heating demand, or hotter summers with higher cooling load. During these periods, power demand is met predominantly by dispatchable power plants and using various flexibility measures. These events can also lead to temporary and briefly higher prices on the wholesale markets if supply is tight. Having sufficient (low-emissions) dispatchable capacity and long-duration storage, among other flexibility options such as demand-side flexibility and interconnections, is important to effectively manage such periods.
In November and December 2024, there were several occasions in Northern Europe when combined wind and solar PV electricity generation was very low, the so-called compounded VRE droughts or
Dunkelflaute events, which led to tighter supply and several hours of extremely high electricity prices on the wholesale markets. In
5-7 November and
11-12 December Germany and the surrounding regions were affected. In early 2025, on
8 January, the United Kingdom had a relatively localised
Dunkelflaute that lasted for about a day. Low wind availability during the nighttime combined with interconnector unavailabilities, power plant maintenance outages and elevated electricity demand led the national energy system operator (NESO) to issue a
notice due to low system margins.
All these events were managed successfully without any impact on the supply of electricity, showing the resilience of the power systems and the underlying market mechanisms. The price spikes observed during the period of a few hours only had a very limited impact on average prices but acted as important signals to incentivise flexible generators to produce more and for flexible consumers to reduce their consumption, while also facilitating the efficient import and export of electricity. Nevertheless, a comprehensive understanding of such events is important to plan accordingly as both electricity supply and demand become more weather-dependent.
IEA (2025),
Electricity 2025, (Page 56,
Spotlight: Dunkelflaute events as potential stress tests) IEA, Paris
https://www.iea.org/reports/electricity-2025, Licence: CC BY 4.0
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