Energy Update #4: extreme heat, energy under pressure

Energy Updates by Energia Corrente × eNextGen — the data, trends and news that really matter to understand the world of energy.

Italy is going through the fourth heat wave of the season, the most intense and the longest of the summer: the Ministry of Health bulletin for 31 July puts 11 cities on red alert and 12 more on orange. The previous wave, between 15 and 22 July, took the Noto station, in the province of Siracusa, to 46.5 °C on its hottest day — the eNextGen team happened to be there in those very days. According to SIAS, the regional agrometeorological service, it was the second most intense heat wave in Sicily in the past 25 years, surpassed only by that of July 2023.

These are not isolated episodes. According to the Copernicus Climate Change Service, June 2026 was the warmest June ever recorded in western Europe, with an average temperature of 20.74 °C: +3.06 °C compared to the 1991-2020 average. Globally, it was the second warmest June ever observed.

Extreme heat does not only change our days. On the power system it acts on three fronts at once: it increases demand, it can limit part of generation, and it puts pressure on prices in the most critical hours. After the 2025 electricity review and energy security, we therefore turn to a form of resilience that is becoming increasingly decisive: climate resilience.

What is really changing in heat waves

What distinguishes this summer’s heat waves from those of ten or twenty years ago: intensity, duration, frequency, night-time minimum temperatures?

“Over the past twenty years heat waves have become more frequent, longer and more intense. We speak of a heat wave when, for at least five consecutive days, it is much hotter than normal in a given place at that time of year: the anomaly is not a fixed number that is the same across Italy, but is measured against what that area has experienced over the past thirty years. Technically, a heat wave is defined as such when temperatures exceed the 90th percentile, that is, levels that in past decades occurred only 10% of the time. The problem is not just daytime heat: increasingly often temperatures do not drop at night either, with so-called tropical nights, when the thermometer stays above 20 °C and, by now often, above 25 °C. Making things worse is the sea, which this year too shows anomalies of up to 5-7 °C above normal: a sea this warm no longer helps cool the air at night as it usually would, and it is one of the reasons why the heat gives no respite even after sunset. Not to mention that a sea this warm also brings other negative impacts, at ecosystem level and in terms of the energy available in the atmosphere for storms or passing weather systems.”

Why is a close succession of four waves more significant than a single absolute record?

“A single absolute record, however significant, can in part fall within the normal meteorological variability intrinsic to the atmosphere: it is an isolated event and remains such. Having four heat waves within the first ten days of August, in the same season, tells a different story: it can be described as a systemic change, one that generates a series of interlinked impacts. The close succession of heat waves puts vegetation and water resources under stress, with an increase in evapotranspiration that leaves vegetation suffering and agriculture in difficulty. Wildfire risk also grows, water availability falls, and the energy question worsens, between demand peaks and reduced supply.”

How does one correctly distinguish an extreme event from a climate trend?

“An event is defined as extreme on the basis of an analysis of the data recorded to describe it: temperature, wind gusts, rainfall accumulation. When those data exceed the typical climatology of a territory we can speak of an extreme event; it is, in a sense, an event that is not expected in that place. A climate trend is quite different. A weather event is a single phenomenon, tied to the meteorological variability of the moment, what happens above our heads; a climate trend instead analyses how meteorological variables behave over a much longer time span: the World Meteorological Organization sets at least thirty years of data as the basis for calculating a climate average, which then becomes the reference. A single event, therefore, cannot on its own determine a climate trend. The opposite, however, is true: a single weather phenomenon, such as a heat wave or a record set within it, can fit perfectly into a climate trend already under way, the one towards warming and the intensification of extremes that we are observing.”

When cooling stops being about comfort

Extreme heat is not only a climate or energy issue: it is also a health risk. EuroMomo has detected an increase in all-cause mortality in Europe from week 26 onwards, noting that the most recent data are still subject to revision.

The point, for those working in energy, is that these numbers move cooling from the category of comfort to that of essential services. An air conditioner, in a flat where an elderly person lives during a heat wave, performs the same protective function that in winter we attribute to heating. It is worth recalling, for completeness, that on a global scale cold remains today around 8-9 times more lethal than heat: but it is precisely the ratio between the two that is shifting, and it is to that shift that the energy system will have to adapt.

Heat as a demand factor

On 15 July, between 3 and 4 p.m., power demand on the Italian grid came close to 58 GW: the highest value of 2026 according to Terna’s provisional data, up 4.6% on the 2025 peak. The main driver was air conditioning.

The figure does not only describe higher consumption, but also a change in the shape of the demand curve. Cooling concentrates demand into a few hours and a few weeks of the year, putting generation and distribution networks under pressure at the same time.

To this is added a structural adaptation component that concerns Europe as a whole: in northern countries, historically without air conditioning, cooling demand is growing on a building stock designed to retain heat, not to expel it.

Heat as a supply factor

The less intuitive aspect is that the same temperatures that push demand up reduce available capacity.

In France, during June’s heat wave, EDF had to shut down three reactors and reduce output at eight others, because the temperature of the river water used for cooling reached the limits set by the nuclear safety authority to protect river ecosystems. According to RTE, the French transmission system operator, the overall effect was a reduction of around 6% in available nuclear capacity. These are manageable constraints, which did not compromise coverage of French demand, but they point in a direction: Europe’s thermal and nuclear fleet was sized around hydrological and thermal regimes that are changing.

The impact on renewables is not uniform. Hydropower depends on water availability, rainfall and snowpack, and its annual contribution to electricity generation can vary by several percentage points from one year to the next. Solar and wind are far less sensitive: according to a recent Ember analysis on Southeast Asia, even in scenarios of increasing extreme heat to 2030 the contraction in output would remain contained within 1%.

Against this backdrop, solar is the main counterweight. Again according to Ember, in June 2026 it generated 52 TWh in the European Union, equal to 25% of monthly electricity generation: for the first time it covered a quarter of the European mix. Since the start of the year, 18 member states have set new monthly records for the share of electricity produced from the sun. The overlap between the hours of highest irradiance and those of highest cooling demand is one of the few favourable coincidences in this picture.

What remains open is the evening window, when cooling demand is still high and solar output is already falling. That is where the highest prices form: on 20 July the GME PUN Index recorded an average of €172.56/MWh, with a daily maximum of €221.94/MWh. This is exactly the space storage is called to occupy, and one where Italy, as we noted in the first Energy Update, has one of the largest pipelines in Europe.

What it means for the system

Planning. Extreme heat can push demand up and reduce available generation at the same moment. For this reason it can no longer be treated as an exception, but as a recurring condition to be built into the design of plants and, above all, of distribution networks: that is where the strains of recent weeks have shown up, in the form of voltage drops and local outages.

Flexibility. The problem is not the overall volume of energy required for cooling, but its concentration in specific hours. Storage and smart demand management can spread the load better across the day. Europe’s Electrification Action Plan indicates the scale of the challenge: moving from today’s 55 GW of storage capacity to 200 GW by 2030.

Access to cooling. If cool air becomes a health safeguard, access to it enters the field of public policy. Those who live in inefficient buildings, those who cannot afford the cost of the system or the bill, those who work outdoors are also the most exposed to the effects of extreme heat. Access to cooling thus becomes a new dimension of energy poverty.

“Mitigation is the set of actions that reduce greenhouse gas emissions; adaptation is the set of actions that reduce the impacts of climate extremes. Without mitigation, adaptation measures would never be enough; without adaptation, the impacts of warming would become hard to bear. On buildings and cities, the good news is that there are many actions and technologies to deploy: external solar shading, light colours and thermal insulation; urban greenery and green or reflective roofs; depaving of courtyards, shared areas and public spaces.”

— Serena Giacomin

What to watch in the coming months

Three elements deserve attention in the weeks ahead.

The first is how August unfolds: with four waves already behind us and a fully summer month still ahead, the demand peak of 15 July may not be the year’s maximum.

The second is the response of storage: hourly data over the coming weeks will show how much the new capacity is contributing to reducing evening peaks and integrating solar output.

The third is how climate conditions evolve next year. Several forecasting centres indicate the development of a significant El Niño event between the end of 2026 and 2027: if confirmed, its effect on global temperatures would add to the underlying trend, with direct consequences for the cooling loads of coming summers.

Mitigation and adaptation are two uses of the same infrastructure

For years, climate was treated in energy analysis as an external variable. The summer of 2026 is showing us that extreme heat is today an element that enters directly into the functioning of the power system: from demand, to generation, to prices. And it calls for design answers, not emergency ones.

From this perspective, the energy transition has a dual function. It reduces the emissions that drive global warming, and it provides the tools — solar, storage, efficiency and flexibility — to live with the share of warming that is by now unavoidable.

Sources: Copernicus Climate Change Service, monthly bulletins on European and global temperatures, June 2026; Terna, provisional data on the peak demand of 15 July 2026; Ember, A quarter of EU power came from solar for the first time in June; EuroMomo, excess mortality monitoring, week of 22-28 June 2026; RTE and EDF, nuclear unavailability due to river temperatures; SIAS – Sicilian Agrometeorological Information Service; Ministry of Health, heat wave bulletin of 31 July 2026; Gestore dei Mercati Energetici (GME), PUN trend, July 2026; European Commission, Electrification Action Plan, 17 July 2026.

This Energy Update is co-written with Serena Giacomin, scientific director of Italian Climate Network, and produced in collaboration with the editorial team of Energia Corrente, where it was first published on 5 August 2026. Read the original version.

Nicolò Golinucci PhD is co-founder and CEO of eNextGen, an official spin-off of Politecnico di Milano that quantifies sustainability and turns it into a competitive advantage for companies.