Energy think tank Ember’s new report highlights the impact of extreme summer temperatures on the grid and the role record solar output played in maintaining grid stability.
The report focuses on four countries; France, Spain, Italy and Hungary, analyZing the impact of June-July 2026 heatwaves and drought on power demand, generation and prices.
According to Ember, during heatwaves beginning in late June, daily power demand increased by as much as 28% in Italy, 23% in Hungary, 14% in France, and 13% in Spain. This is compared to the week preceding the heatwaves (13-19 June), when temperatures were closer to normal seasonal averages.
The high temperatures resulted in increased demand from air conditioning requirements, while simultaneously disrupting hydropower and nuclear output.
Supply scarcity
Europe, in this case, experienced record solar output together with the increase in temperatures. This, states Ember in the report, helped cover increased demand during daylight hours, with high prices and supply scarcity most pronounced in the evenings.
Solar production was up to 17% higher on heatwave days compared to other days in June and July, which not only helped stabiliZe the grid, but also mitigate the disruptions caused to other generation sources.
Specifically, European hydropower production was at its lowest level in at least a decade for May, June and July. Also, states the report, in Hungary and Romania, record low Danube water levels sharply reduced output from the countries’ only nuclear power stations, which typically provide 40% and 15% of their respective electricity generation.
Ember suggests complete shutdowns may be necessary if water levels do not recover.
These impacts on power generation sources have led to a dramatic rise of electricity prices, with early evening peak prices in some markets reaching their highest levels since the 2022 gas crisis.
Dr Chris Rosslowe, senior energy analyst at Ember, commented on the findings: “Solar is already doing heavy lifting during heatwaves, but the real challenge starts after sundown.”
System resilience
Rosslowe points to battery storage as one the clearest paths to a more resilient power system in hot summer months.
“As solar performs during heatwaves while other power sources struggle, storage can carry cheap electricity into the evening, when cooling demand is still high and the grid is most exposed to expensive thermal power.”
The fact that increased solar generation could help limit price increases during daylight hours, but not in the early evenings, shows a lack of flexibility, says Ember.
Flexibility can be sourced from battery storage, demand response or interconnectors between countries or regions.
Ember points to battery storage as being well suited to answering the flexibility question, stating that “additional storage could shift low-cost solar power into the evening, better aligning supply with cooling demand and reducing reliance on expensive thermal generation.”
Originally published in Factor This sister publication Enlit World.
Facts Only
* Ember is an energy think tank.
* Analysis covers France, Spain, Italy, and Hungary.
* Heatwaves occurred in June and July 2026.
* Daily power demand increased by 28% in Italy, 23% in Hungary, 14% in France, and 13% in Spain.
* Comparison baseline is the week of June 13-19.
* Solar production was up to 17% higher on heatwave days compared to other June and July days.
* European hydropower production for May, June, and July was at its lowest level in at least a decade.
* Low Danube water levels reduced nuclear output in Hungary and Romania.
* Nuclear power typically provides 40% of electricity generation in Hungary and 15% in Romania.
* Early evening peak electricity prices reached levels comparable to the 2022 gas crisis.
* Potential flexibility sources include battery storage, demand response, and interconnectors.
Executive Summary
Extreme summer temperatures in 2026 created a dual pressure on European power grids by spiking cooling demand while simultaneously impairing traditional generation sources. In Italy, Hungary, France, and Spain, power demand rose significantly—up to 28% in some regions—driven by air conditioning requirements. This surge coincided with a decade-low in hydropower production and reduced nuclear output in Hungary and Romania due to critically low Danube water levels.
Solar energy acted as a primary stabilizing force, with production increasing by up to 17% during heatwave days, effectively covering demand during daylight hours. However, this created a flexibility gap; as solar output drops after sundown, the grid remains exposed to high cooling demand and expensive thermal power, leading to price spikes in the early evenings. While battery storage, demand response, and interconnectors are identified as solutions to shift low-cost solar energy into peak evening hours, the current lack of such flexibility leaves the system vulnerable to price volatility and potential shutdowns if water levels do not recover.
Full Take
The strongest version of this narrative is a cautionary tale of the "energy transition gap": the period where renewable generation is sufficient in volume but insufficient in flexibility. It correctly identifies that while solar scales perfectly with heat-driven demand, the absence of storage transforms a resource abundance into a timing crisis.
The logic follows a linear path: Heat $\rightarrow$ Demand Up / Hydro-Nuclear Down $\rightarrow$ Solar Gap at Night $\rightarrow$ Price Spikes $\rightarrow$ Storage Solution. This framing presents battery storage not just as an upgrade, but as the singular critical path to resilience. By focusing on the "heavy lifting" of solar and the "challenge" of sundown, the narrative effectively narrows the solution set to storage and interconnectors, potentially underselling the role of diversified baseload or aggressive demand-side management.
The driving paradigm is one of systemic fragility. It assumes that the primary bottleneck to grid stability is storage capacity rather than regulatory hurdles or aging infrastructure. The second-order consequence is that the financial viability of the energy transition becomes tied to the speed of battery deployment; without it, "green" energy may be perceived as unreliable during the exact moments of peak crisis.
Patterns detected: none
If this were an influence campaign, the playbook would involve highlighting a climate-driven crisis to create urgency (Fear Appeal) and then positioning a specific technology—likely from a storage vendor—as the only viable rescue (False Binary). However, the content here is a general think tank analysis of grid mechanics; it identifies a systemic need rather than pitching a specific product. It remains a technical observation of a structural vulnerability.
Bridge Questions:
1. How does the cost of deploying massive battery storage compare to the cost of maintaining traditional baseload plants during extreme weather?
2. To what extent would "demand response" (incentivizing users to shift usage) mitigate the evening peak without requiring new hardware?
3. Are there alternative cooling technologies for nuclear plants that would make them less dependent on river water levels?