Da solen forsvant: Slik sendte en solformørkelse og hetebølge europeiske strømpriser til himmels

Heatwave simultaneously crushed other supply sources

Extreme temperatures constrained French nuclear output because high river-water temperatures limited cooling capacity, and suppressed German wind generation as calm conditions settled in . Spot prices had already jumped more than 20% in the days preceding the eclipse . The heatwave also reduced the efficiency of combined-cycle gas turbines (CCGTs), meaning even fast-ramping backup plants were not operating at full capacity .

Cooling demand spiked

The heatwave drove up electricity use for air conditioning and refrigeration, compounding the supply squeeze . Day-ahead prices had already surged 21.8% in France to €142.5/MWh and 22.8% in Germany to €138.5/MWh by August 11 .

The result: a near-perfect supply-demand pincer

Less solar + less nuclear + less wind + more demand created a shortfall that wholesale markets resolved at extreme prices. Fast-ramping backup (gas turbines) was already stretched by the prolonged heatwave conditions .

What this reveals about grid vulnerability

Solar dependency creates acute timing risk

Europe has added massive solar capacity in recent years, but when an eclipse knocks it out during a narrow, high-demand window, the system needs rapid substitutes. The fact that prices briefly doubled in 15 minutes shows how thin the slack is during such events . The eclipse's timing — during the evening ramp when solar output is already falling — was particularly unforgiving.

Extreme heat compounds renewable intermittency

Heatwaves do not just raise demand for cooling. They also degrade nuclear output (through thermal discharge limits on river water used for cooling), reduce gas turbine efficiency, and can coincide with low wind speeds . This means the usual backup sources are also impaired when they are needed most.

Short-term volatility is high, but system stability held

The European Commission's Electricity Coordination Group confirmed that there were no short-term adequacy risks and the system remained stable, though the situation was "expected to remain tight" . Cross-border coordination and the single EU electricity market helped keep the lights on, but prices bore the full stress .

This is a preview of a growing problem

As Europe's power mix becomes more weather-dependent, the gap between average prices and extreme-event prices will widen unless there is much more dispatchable storage, demand response, and interconnector capacity to smooth out these minutes-long supply shocks. The eclipse event is a stark reminder that the energy transition must include not just renewable generation, but also the flexibility to manage moments when the sun and wind disappear simultaneously.