Feeling the Heat: Preparing Europe's Grids for Summer

Europe’s electricity grids are feeling the heat. Extreme temperatures raise conductor resistance and force thermal plants—nuclear, coal and gas—to shut down when cooling water becomes too warm. This physical reality, combined with soaring air‑conditioning demand, creates a double‑whammy: higher load and fewer available generators. Operators also grapple with reduced hydro output during droughts, amplifying the stress on an already strained system. The convergence of these factors makes heat‑wave resilience a top priority for policymakers and market participants alike.

At the same time, renewable capacity is expanding faster than the transmission network can accommodate. Solar farms can be built in months, yet new high‑voltage lines require decades. The resulting bottlenecks—often described by German terms like "Dunkelflaute" and "Hitzelflaute"—mean that during hot, wind‑quiet periods, the grid relies on fossil backups. Flexibility resources such as demand‑response, battery storage and long‑duration energy storage are emerging as critical tools. Modern batteries now offer four‑hour to eight‑hour discharge durations, providing both frequency response and inertial support traditionally supplied by fossil generators.

Despite rapid technology advances, Europe still faces gaps in speed and financing. Schemes like the UK’s Long‑Duration Energy Storage programme aim to commercialise multi‑hour batteries and pumped hydro, but widespread deployment remains limited. Grid congestion, lengthy permitting processes, and the need for ancillary services impede the transition to a zero‑carbon hour of operation. Accelerating grid reinforcement, streamlining market rules, and scaling long‑duration storage will be essential to keep lights on as heatwaves become the new normal.