When heavy storms triggered a fault on a major power line in Indonesia’s Sumatra in late May, blackouts plunged homes and businesses across the island into darkness, leaving millions to cope without power in the humid heat for up to a day.

Failed traffic lights caused chaos on the streets of Medan, one of the country’s biggest cities, and restaurants and shops had to shutter or throw out food after fridges stopped working. Four people were reported to have died from carbon monoxide poisoning from generators.

A power outage caused by damage to cables on a high-voltage transmission line, the first of two to strike Sumatra in a fortnight, highlighted the huge challenge facing Indonesia and much of neighbouring Southeast Asia – the maintenance and upgrading of inadequate grid capacity that industry analysts say is proving an obstacle for billions of dollars in planned clean power investments.

Experts told Climate Home News the Galang–Simangkuk transmission line, which was relatively new and only began operating seven years ago, should have been able to withstand the storms that caused transmission towers to collapse in early June.

“It should not have had these grid failures,” said Wai-Shin Chan, Hong Kong-based head of research at Asia Research & Engagement, a consulting firm, warning that climate change would bring more frequent episodes of extreme weather.

“The grid resilience is really not there,” Chan said.

The Indonesian Air Force helped state-owned utility PT Perusahaan Listrik Negara (PLN) transport emergency power towers to restore electricity supplies within 24 hours, but the two incidents could cause longer-lasting damage to investor confidence – hurting the delivery of much-needed reliable clean electricity supplies.

PLN did not respond to a request for comment.

Grid bottlenecks and projects stuck on hold

With electrification high on the agenda of the COP31 climate talks later this year, there is growing global focus on the need to bolster grid infrastructure to cope with increased electricity use and more renewables in the power mix.

In Southeast Asia, energy experts say inadequate grid capacity and maintenance is already proving a major factor in the region’s stuttering rollout of new clean energy projects.

About 50% to 60% of renewable energy projects in Vietnam, Thailand and Indonesia were cancelled or stalled between 2021 and 2025, according to a recent report by consultancy Bain & Company and Standard Chartered. In Indonesia, 48% of announced projects were subsequently dropped or delayed during that period.

Progress in the region is also being hampered by issues ranging from unclear power purchase agreement (PPA) structures, a failure of power policies to keep up with investor needs, permitting and licensing approval delays, grid connection constraints, limits to private sector involvement in electricity markets, and policy and tariff uncertainty, energy experts said.

Some renewable energy projects have also faced opposition due to their environmental impact and issues related to land rights.

But Bain researchers found grid infrastructure was the biggest bottleneck for Southeast Asia’s energy transition, with about $18 billion per year needed in investment for modernisation and upgrades.

The International Energy Agency (IEA) has warned that electricity grid and storage investment in the region was higher in 2015 at $15 billion compared with $12 billion in 2025, even as electricity demand and renewable energy growth accelerated.

“It’s a concern for long-term power development in the region,” Chan said.

“If these risks – grid curtailment, policy uncertainty, permitting and PPA – are not adequately addressed, investors just don’t have the confidence to hit the final investment decision button,” he added.

A stuttering energy transition

Ramping up progress on solar, wind, hydro and geothermal projects is vital for Southeast Asian nations to hit their targets on cutting planet-heating carbon emissions.

Indonesia has pledged to reduce emissions by 31.9% by 2030 compared with business-as-usual levels, or by 43.2% with international support, on the way to reaching net zero by 2060.

Renewables accounted for about 18% of Indonesia’s energy mix in April 2026 according to local media reports, falling short of the country’s initial 23% target for 2025, with the majority of its energy needs met by coal, oil and gas. In 2025, a new National Energy Policy postponed achieving the target to 2030.

“The region carries significant weight in global terms, given its share of world population and energy consumption,” said Joseph Jacobelli, an impact investor and author of Asia’s Energy Revolution and Powering the Unstoppable Green Shift.

“Every delay in renewable energy deployment extends dependence on fossil fuels and pushes net zero targets further out of reach,” he said.

There are cost benefits of increasing renewables in the overall power mix, too.

In many parts of the region, new renewable power – especially solar and onshore wind – is cheaper than building new fossil fuel generation. The global energy shock unleashed by the Iran war has highlighted the energy security benefits of renewables, though it also raised concerns about coal backsliding in countries including Indonesia.

Surging oil prices exposed Southeast Asia’s vulnerability to fossil fuel supply disruptions, causing energy prices to soar and widespread fuel shortages that led the World Bank to downgrade the region’s growth projection.

“This situation pushes us to accelerate [the energy transition], we must move faster,” Indonesian President Prabowo Subianto said in March, adding that the government was focused on solar projects that would deliver a total installed capacity of up to 100 GW.

At the same time, progress on moving away from coal has been sluggish. Both Indonesia and Vietnam signed up for Just Energy Transition Partnerships (JETPs) – a funding initiative set up by the G7 to help developing nations shift away from coal – though a lack of favourable financing is holding back these plans.

The US withdrew from its JETP deals with the two countries last year, reflecting President Donald Trump’s wider energy policies, and Indonesia abandoned plans to close a major coal power plant.

Lack of finance, or lack of faith?

But a shortage of financing to bring new renewables projects online is not the cause of foot-dragging in Indonesia, where installed solar capacity reached only about 20% to 30% of the government’s 2020-2025 target, Bain researchers said.

Of an estimated $540 billion in green capital expenditure announced across Southeast Asia’s power and electric vehicle value chains between now and 2030, only about $315 billion is on a credible path towards deployment under current conditions, according to the report.

Between 2022 and early 2026, more than a quarter of the 452 new solar projects announced in Southeast Asian countries were postponed or cancelled, according to Global Energy Monitor‘s Global Solar Power Tracker.

In Indonesia, the Batam Bintan Karimun solar farm was initially expected to come online by 2024 but was cancelled in 2023 for unknown reasons, Kasandra O’Malia, a project manager at Global Energy Monitor, told Climate Home. The project also included plans for Southeast Asia’s largest associated battery storage facility.

Another high-profile Indonesian development that has stalled is a 3,500 MW solar and storage project proposed on Riau Island to export clean electricity to Singapore. While not formally abandoned, there have been few updates to this project since April 2022.

“This execution gap is not really to do with money – there is available capital – but the finance is not being deployed effectively because the risks have not been adequately redressed,” Chan said.

In a bid to foster investor certainty, Indonesia’s government approved a new 2025-2034 Electricity Supply Business Plan (RUPTL) for PLN in May 2025, replacing years of delays over the country’s power development roadmap.

As well as aligning government policy, streamlining permitting, simplifying purchase procedures and targeting 70 GW of new generation, with renewables accounting for the vast majority of additions, the plan includes the construction of about 47,800 kilometres of new transmission lines and substations with a total capacity of 108,000 megavolt-ampere, spread across Indonesia.

The Ministry of Energy and Mineral Resources, several domestic and international renewable energy developers, and the Indonesia Renewable Society, did not respond to requests for comment.

Another way to soothe investors’ nerves would be for governments to use public money to de-risk investments, but there is little appetite for this approach in the region, Chan said.

A more effective tool would be ensuring stable, investment-friendly energy market policies and regulations, said Alnie Demoral, a Manila-based energy analyst at climate think-tank Ember who previously worked with solar developers and investors.

Renewable energy developers, investors and authorities can spend years negotiating the project’s costs, permitting and whether grid connection will be available to bring clean power online, she said.

Often the longest discussions focus on the power pricing tariffs that governments set for renewable energy producers. Changing policies or disagreement on underlying cost assumptions can stall or delay a project before it reaches financial close, she added.

“Governments have to do their part by making sure the investment environment is stable,” Demoral said.

“But this is a two-way process. The private sector and developers must also ensure that their assessments of the project are based on robust assumptions.”

AI data centres add to the strain

At the same time, rapid growth in power-hungry AI data centres is putting extra strain on the region’s overstretched grids.

AI data centres, which use much more power than regular data centres, are becoming one of the largest drivers of new power demand in Southeast Asia as governments in the region jostle for more multibillion-dollar investment in the sector.

The slow pace of renewable energy deployment and grid modernisation, coupled with ongoing reliance on fossil fuels in the electricity mix, will make it difficult for the region to meet a new, fast-growing source of additional demand without increasing emissions.

Emissions from data centre power use in Indonesia are expected to quadruple between 2024 and 2030, according to Ember.

AI data centres operate around the clock and will often use any power that is available – be it renewables or fossil fuels, said Chan, urging policymakers to first ensure they can meet the power needs before courting data centres.

Many new AI data centres are planned for areas with insufficient high-voltage transmission capacity, according to the Bain report, suggesting that countries should focus on new high-voltage lines, larger substations and stronger interconnections between regions.

The researchers note that AI data centres also typically take about one to three years to build, while major electricity transmission lines and grid updates can take five years or more, adding that power grid investments must happen before renewable energy or AI projects.

“Growth in data centres and AI is already adding pressure to constrained grids,” said Christina Ng, the Kuala Lumpur-based co-founder of Energy Shift Institute, an Asia-focused, independent energy finance think-tank.

“The risk is that new demand is met through high-emitting electricity if clean power and clean grid investment do not keep pace.”

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Main image: A technician walks next to solar panels that partially provide electrical power to the Grand Mosque of Istiqlal in Jakarta, Indonesia (Photo: REUTERS/Willy Kurniawan)

The post Southeast Asia’s fragile grids threaten billions in clean energy investment appeared first on Climate Home News.

Southeast Asia’s fragile grids threaten billions in clean energy investment

Benito Müller, Anju Sharma, Jen Allan, Matthias Roesti and Luis Gomez-Echeverri.

Every November, tens of thousands of people descend on the world’s annual UN climate conference. Presidents and prime ministers, negotiators, business executives, campaigners, journalists, celebrities and lobbyists converge on one city for two frenetic weeks, all convinced they need to be there.

Everyone with a stake in climate action feels they must be present. Any suggestion of a smaller, more focused conference is quickly met with concerns about exclusion. But it is time to ask an uncomfortable question: has the fear of missing out (FOMO) become one of the biggest obstacles to effective international climate cooperation?

The story in numbers

When governments first met under the UN Framework Convention on Climate Change (UNFCCC) in the 1990s, the annual Conferences of the Parties (COPs) attracted only a few thousand participants. Even the Kyoto conference, which produced the first legally binding emissions agreement, hosted fewer than 10,000 people.

Since then, analysis by ecbi reveals a striking trend: after each major treaty COP, the participation at the next COP approximately doubled (see chart below).

Why?

Part of the answer is success. As climate change has risen up the political and economic agenda, more actors quite rightly want to engage. But our analysis reveals that a less acknowledged force is also driving the spikes in participation: FOMO.

As more heads of state attended, ministers concluded they had to be there too. As ministers arrived in greater numbers, government delegations expanded. Businesses, investors, researchers, campaigners, journalists, city leaders and philanthropies reached the same conclusion: if everyone important is going to COP, we cannot afford to stay away.

The result is a self-reinforcing cycle. The larger COP becomes, the more indispensable attendance appears, because presence signals relevance.

The negotiating community has barely grown

The headline attendance figures tell only part of the story. At COP28, more than 42,000 Party badges were issued to official national delegations. However, only 1,581 delegates had also attended the technical negotiating session in Bonn just five months earlier. Fewer than 4% of Party delegates formed the core negotiating community.

Comment: The UN climate process was built for negotiation – now it must support implementation

This core negotiating community has remained remarkably stable: across the five COPs since Paris, between roughly 1,300 and 1,600 delegates consistently attended both the June negotiating session and the annual COP.

The negotiating community has not become twenty times larger, but the COP has.

One COP, three different events

Today’s COP has, in fact, evolved into three very different events rolled into one.

The first is the formal negotiating session, where governments agree rules, guidance and decisions under the Convention and the Paris Agreement.

The second is a global political summit, where leaders announce initiatives and demonstrate political commitment.

The third is a vast climate expo, where businesses, cities, researchers, financial institutions and civil society showcase solutions, build partnerships and engage the public.

Each of them serves a valuable purpose, but the problem is that they have become bundled together by historical accident rather than institutional design.

Bigger is not always better

The consequences of “mega-COPs” are becoming increasingly difficult to ignore.

The countries most vulnerable to climate change are increasingly less able to host COPs and thus lose the ability to have their voices properly heard. Hosting a modern COP now requires enormous financial resources, extensive security operations and accommodation capacity that many countries simply do not possess. Even wealthier nations have become more reluctant to take on the burden.

Inside the venue, size creates its own inefficiencies. Climate negotiations often advance through informal conversations: a chance meeting in a corridor, a discussion over coffee, an impromptu conversation between delegates who discover common ground. Those opportunities become rarer when participants spend hours navigating enormous venues and crowded security checkpoints.

Comment: COP presidencies should focus less on climate policy, more on global politics

Observer access is constrained by overcrowding. National delegations increasingly include large numbers of non-government participants, sometimes outnumbering officials from government ministries. Meanwhile, businesses, campaigners and journalists compete with negotiators for the same space and attention.

The very scale of the event also creates a reputational problem. A gathering of 60,000 or more people inevitably creates expectations of dramatic political breakthroughs every year. Yet much of today’s climate diplomacy involves steady, technical progress. When those quieter achievements are judged against the expectations generated by a mega-event, disappointment in the UN climate change process becomes almost inevitable.

Time to unbundle

Not everything must happen in the same place at the same time. Negotiations, political leadership and implementation partnerships each deserve their own space. They should become separate events.

Routine governing body sessions, involving the roughly 5,000 participants directly engaged in the formal process, could be held in Bonn, where the UN climate secretariat is based. Political summits could be convened separately when leaders’ intervention is genuinely needed. Climate expos could continue to rotate with the COP Presidency, providing dedicated opportunities for businesses, investors, cities, researchers and civil society to showcase solutions and forge partnerships.

Such an approach would strengthen, not weaken, participation. Negotiators would benefit from a more focused and effective working environment. Host countries would face a far more manageable logistical and financial challenge. Climate-vulnerable countries would once again have a realistic opportunity to host key meetings and shape the global agenda. Businesses, investors, cities and civil society would gain greater visibility by engaging in forums designed for partnership, innovation and implementation, rather than competing with formal negotiations for space and attention.

Comment: Not another COP-out: We must rewrite the rules of the UN climate talks

Today’s mega-COPs evolved incrementally, one seemingly sensible decision at a time, until their sheer scale began to undermine many of the objectives they were intended to serve. The fear of missing out now risks becoming one of the biggest barriers to the reforms needed to make the process more effective.

The greatest fear now is not missing out on the next COP, but missing the opportunity to redesign the process so it can deliver on its ultimate purpose: tackling the climate crisis.

Benito Müller is managing director of Oxford Climate Policy and director of the European Capacity Building Initiative (ecbi).

Anju Sharma is a climate policy specialist with Oxford Climate Policy.

Jen Allan is a senior Lecturer at Cardiff University and strategic advisor at the International Institute for Sustainable Development.

Matthias Roesti is a postdoctoral researcher studying the political economy of climate change at the University of Pennsylvania’s Environmental Politics Lab.

Luis Gomez-Echeverri is a former senior staff member with UNDP and UNFCCC and currently an emeritus research scholar at the International Institute for Applied Systems Analysis, working at the intersection of climate and development.

The post Is FOMO undermining climate diplomacy? appeared first on Climate Home News.

Is FOMO undermining climate diplomacy?

Heatwaves are becoming more likely and more intense due to climate change, impacting sources of power generation around the world as they work to meet increased demand.

When temperatures soared past 40C in parts of Europe in June and July 2026, nuclear reactors shuttered, gas plants’ efficiency fell, wind speeds dropped and electricity networks sagged.

Yet, while all types of electricity generation are affected variously by extreme heat, some commentators are quick to point the finger at “intermittent” wind and solar, while downplaying the impact on sources such as gas or nuclear power.

Extreme heat also drives up electricity demand, as people turn on air conditioning and fridges work harder.

For example, in France, daily electricity demand rose by almost 20% during a two-week heatwave in June 2026.

This often leads to an increase in power prices, as generation strains and demand rises, putting a premium on electricity.

Below, Carbon Brief – amid a slew of misleading claims – explains how key power sources cope with extreme heat.

Nuclear

The impact of heatwaves on nuclear power generation is well documented, with a plethora of headlines often accompanying record temperatures in nations that rely on the technology.

For example, around 70% of electricity is generated by nuclear power in France, leaving it vulnerable to the impacts of heatwaves.

During the July 2026 heatwave, three of France’s 57 nuclear reactors had to shut down. Generation was reduced at another seven, causing an almost 9% dip in power production.

(This is a well-known phenomenon – France has seen reductions in nuclear generation due to heatwaves in 2003, 2006, 2015, 2018, 2019, 2022 and 2025.)

A similar story is true across various countries in Europe. Low river levels on the Danube have hit nuclear reactors in Romania, Hungary and Serbia this summer, while a Swiss nuclear reactor shuttered due to high river temperatures.

It is nuclear plants using river water to cool their reactors that are most significantly affected by heatwaves and droughts. These make up 14% of the global fleet. Around 60 of the world’s 440 river-cooled reactors are located in France, with a further seven across Europe.

Nuclear power plants use fission to generate heat, which is used to create steam. This steam spins the blades of a turbine that is connected to a generator to create electricity.

Following this process, the water is cooled to allow it to be recycled back through the system as steam again. Nuclear power plants generally use water from rivers or the sea to help cool and condense this steam.

As such, when water temperatures rise due to a heatwave, their cooling capacity is reduced and the overall efficiency of the nuclear power station is affected. Similarly, if there is less water available due to drought, they cannot be cooled as effectively.

Michael Tadrous, a researcher at McMaster University’s DeGroote School of Business in Canada, tells Carbon Brief that the “impact [of heatwaves] is real, but it is far smaller than many headlines suggest” and that the “effect [of heat] is gradual”. He adds:

“Warmer intake water makes a reactor slightly less efficient. [But] even an extreme 15C rise in cooling-water temperature would cost a large reactor only about 6% of its output.

“The real pressure point during a heatwave is usually legal rather than technical. Plants return their cooling water to the river a few degrees warmer than they drew it and the law limits how warm that water may be in order to protect aquatic life.”

Henry Preston, a spokesperson for the industry body the World Nuclear Association, adds that reactor shutdowns due to high river temperatures are “typically an automatic response to comply with regulations to protect local ecosystems, rather than a technological fault”.

He notes that in some extreme heatwaves, these regulations are waived given the “essential need for electricity and taking a proportional approach to climate risks”.

While nuclear power plants can generally return to standard operation quickly if they have been affected by high water temperatures, drought can cause a more significant impact.

Preston tells Carbon Brief:

“In contrast to high river temperatures, which can quickly return to acceptable levels once a heatwave passes, low river levels can persist for much longer, if drought conditions continue. As a result, low water levels may have a more prolonged impact on plant operations than elevated water temperatures.”

This is set to be the case in the current European drought, where multiple reactors in Hungary and Romania have shut down or reduced their output due to low water levels.

The Danube is not expected to return to normal water levels for “days or even weeks as no significant rainfall is forecast”, reported the Associated Press on 3 August 2026. It said this was “push[ing] some countries in eastern Europe to the brink of energy emergency”.

While heatwaves and drought can produce significant short-term effects, their impact on the availability of nuclear power across a full year is generally minimal.

On average, heatwaves cut annual nuclear generation by 0.6% between 2003 and 2022, according to a recent study that Tadrous co-authored.

He adds that, across the whole period studied, the only time a national nuclear fleet lost more than 1% of its nuclear power over a year to heat- and drought-related curtailments was France in 2003, which lost 1.3%.

According to an article in Forbes, for every additional degree Celsius in temperature, a nuclear power plant loses around 0.6-1% in cycle efficiency.

To minimise the impact on both energy security and costs, governments and nuclear companies are looking at a range of solutions to adapt to heatwaves.

For example, French nuclear-plant operator EDF is looking at additional cooling towers for its sites that are the most exposed to the impacts of a warming climate, reported Bloomberg recently.

Tadrous says the nuclear power industry is already adapting to heatwaves that are “more frequent and more intense”, adding:

“France’s river-cooled fleet lost 5.5 terawatt hours (TWh) of output to the 2003 heatwave. By 2022, one of the most severe heat-and-drought summers on record, losses had fallen to 0.5TWh, a reduction of roughly 90%, as utilities upgraded cooling systems, refined operating practices and scheduled maintenance around periods of extreme heat.”

There remain challenges for adapting nuclear power – and the wider electricity systems in which it sits – to heatwaves. However, Tadrous notes that this is less about “technical feasibility than of economic prioritisation and timely implementation”.

Gas

Gas power plants have a reputation for being reliable and able to switch on at any moment, sometimes referred to as “firm, dispatchable” capacity.

Yet, as a type of thermal generation, they are subject to many of the same stresses during heatwaves as nuclear power.

An article by the science advocacy organisation Union of Concerned Scientists (UCS) notes that the “purported ability of gas plants to be available at all times to generate electricity, particularly when the grid needs it most, is increasingly under scrutiny” due to heatwaves.

As a matter of physics, the efficiency of gas power plants drops as temperatures rise. At 40C, a gas-fired power station can expect its capacity to be reduced by 13% and its efficiency by 7% compared to when running at 20C, according to Electric Insights.

Dr Iain Staffell, associate professor in sustainable energy at Imperial College London, tells Carbon Brief:

“Simple gas turbines (the kind which turn on rapidly to meet peak demand) are hit harder [than solar, for example], with their power output falling by about 10% per 10C.”

(He adds that the transmission system struggles more than electricity generation during high temperature. Power line capacity can fall by up to 16% for a 10C rise in temperature, according to a report for the UK government.)

Several types of gas power plants require cooling as part of their process, including gas steam and combined cycle turbines (CCGTs). They usually rely on nearby bodies of water for this.

Additionally, as the UCS article notes, hot air has a lower density than cool air. As gas CCGTs rely on burning a mix of gas and air, this lower density means air takes up more space, leaving less room for gas.

Ultimately, this means that when the air is hot, gas power plants cannot generate as much electricity as normal.

These effects are not just theoretical. For example, across two nights in August 2020, there were rolling blackouts in California, US, as demand exceeded supply amid a heatwave.

While a number of factors contributed to the blackouts, gas plants made up around 79% of the capacity that dropped off the system on 14 August and a similar share the following day.

Amid record-breaking heat in summer 2026, gas power plants have also seen their capacity cut in the UK, France and other countries.

Dr Staffell adds that gas power stations are thought of as “reliable, because of the way we use them” in the UK.

Whereas wind and solar are usually used to the maximum extent possible, he says that on average, only around 40% of the gas fleet is in use at any one time. As such, even if the efficiency of one gas power plant is affected by high temperatures, “we have a lot of slack to call on more of them to run”. He adds:

“The issue is less that they can’t deliver, but we have to pay through the nose to persuade more to turn on at critical times, adding to sky-high energy bills.”

Wind

The impact of heatwaves on wind generation is less direct than for other technologies.

However, wind speeds often drop during heatwaves, which tend to build during periods of sustained high pressure into extreme events such as “heat domes”.

Dr Staffell, explains to Carbon Brief:

“The very hottest days tend to create heat domes with very low wind speeds, which directly reduces the output that windfarms can produce. Air is also less dense the hotter it is, so it carries less energy within it, so there is a double impact on wind turbines.”

High temperatures are linked to low wind speeds across three-quarters of the globe, according to one recent study, looking at data from 1980 to 2023.

The study found that, as a result, across Australia, northern Asia and Europe, wind power decreased by an average of 30-50% during heatwaves.

This is inconsistent globally, however, with the Amazon, the Great Plains in North America and central Africa actually seeing a slight increase in wind during high temperatures.

As such, while the effect of heatwaves on wind generation is less direct than other generation technologies, it can have a significant impact.

In the UK in June 2026, wind generation fell to around 15% of the electricity mix due to low wind speeds, from an average for the month of about 30%, according to Octopus.

Low wind generation during this period was a key feature of the strain on the grid experienced during this time – in particular, as demand rose amid record-high temperatures.

On Wednesday 24 June, for example, the National Electricity System Operator (Neso) had to pay high prices to balance supply and demand. This included paying as much as £1,400 a megawatt-hour to secure around 1.7 gigawatts (GW) of imported power, nearly 20 times the average price for electricity in June 2025.

A Neso spokesperson said in a statement: “This is due to the impact of extremely high temperatures affecting Great Britain and the continent, and low wind.”

While reduced wind generation is common during a heatwave, it is not generally viewed as a concern for energy system operators. This is due to wind following well-established seasonal patterns – it generates less power in summer than in winter – as well as being complementary to other renewable technologies, such as solar.

Dr Chris Rosslowe, senior energy analyst for Europe at Ember, tells Carbon Brief:

“Power systems are less reliant on wind power in the summer months and its lower-than-average output is already expected and planned for. Heatwaves often bring still, but clear conditions, highlighting the benefit of wind and solar as a duo – poor conditions for one often mean good conditions for the other.”

As such, wind power remains one of very few technologies considered “resilient” to heatwaves by the UK government.

However, this did not stop the anti-renewables Daily Mail from attempting to blame the technology for strain on the UK grid on 24 June 2026, despite its own article acknowledging that gas plants had also been forced to cut their output by 2.5GW on the day.

Solar

Another common claim seen in the media is that solar “struggles” during heatwaves, with high temperatures pushing down the technology’s efficiency.

Yet heatwaves tend to coincide with long, cloudless days, when solar generation is reliably above average – despite the impact of high temperatures.

While hot weather does reduce the efficiency of solar cells, the effect is relatively modest – and widely understood. Each 1C of temperature rise reduces output by around 0.4-0.5%, according to a recent study.

This is in line with an evidence review for the UK government, which suggests the performance of solar panels falls by 0.2-0.5% for every degree of heat above 25C.

Generally, however, this effect is easily outweighed by high sunlight hours during hot spells. For example, across a four-day heatwave in the UK in June 2026, solar generated 484 gigawatt-hours (GWh) of electricity – a 46% increase over the same period a week earlier.

Similar generation highs were seen across Europe, amid record temperatures and dangerous heat that was pushing people towards the use of air conditioning.

Solar generated a record 52TWh across the EU in June 2026, beating the high set just the month before of 47TWh.

In fact, solar – especially when combined with battery storage – is a complementary technology to air conditioning, given their similar seasonal patterns. Over the course of the day, demand from air conditioning and generation from solar also marry up well.

Dr Rosslowe says:

“Solar, battery storage and air conditioning are a highly complementary trio of technologies during heatwaves. There’s a high overlap between solar output and demand from AC.”

For example, on the hottest day of the year so far in Great Britain (the island grid serving England, Wales and Scotland), on 26 June 2026, solar surged to 13.9GW in the middle of the afternoon, as demand also hit its highest point, as shown in the chart below.

Across June 2026, homes with solar panels generated the equivalent of five hours of “free” self-supplied air conditioning, according to recent analysis.

Despite the impact of heat on solar efficiency, the technology is, therefore, well placed to bolster energy systems during heatwaves.

Indeed, as Dr Rosslowe tells Carbon Brief, solar suppresses power prices during daylight hours. But, even though it is predictable, there are still challenges around managing the dip in solar generation as the evening sets in. This is often compounded because it coincides with the usual evening increase in demand.

Dr Rosslowe explains:

“Problems arise when the sun goes down, but demand for cooling remains high. In the early evening hours, when gas power typically ramps up to replace solar, we have seen prices spike to extreme levels, made worse by high international gas prices.”

Storage

Energy storage systems are increasingly key to managing the impact of heatwaves on electricity systems.

The category of technologies is dominated by batteries, with more than 108GW of battery storage added in 2025 alone, according to the International Energy Agency.

Already, batteries have been used to take advantage of surges in solar generation during the daytime, amid high summer temperatures.

This is particularly useful to meet evening peaks in electricity demand, as well as the need for air conditioning overnight when temperatures do not fall.

In a statement, Pawel Czyzak , Europe programme director at Ember, said:

“Heatwaves will not go away – they will only get more severe in the future. Solutions that can help mitigate their impacts, such as battery storage, interconnection, demand flexibility and dynamic tariffs, should become a key part of grid planning and power market design.”

However, batteries are not without their challenges during heatwaves. Battery performance also decreases as temperatures exceed their optimal level.

Additionally, high temperatures can accelerate the degradation of components in lithium-ion batteries, which dominate the sector.

Analysis for the UK government found that prolonged operation at very high temperatures could – at least in theory – “overwhelm” the cooling systems built into batteries, “posing risks such as thermal runaway and explosions”. However, it noted that in practice, these cooling systems are “routinely” designed to handle temperatures of up to 45C.

(The analysis added that “developers and manufacturers have a strong understanding of risk to [battery storage systems] from high temperature and mitigate risks through regular maintenance, design improvements, and passive cooling strategies”.)

Other storage technologies also face challenges during heatwaves. For example, pumped hydro storage can be significantly impacted by drought.

Australia – which now has 4.3GW of large-scale battery storage capacity – saw its fleet of batteries and pumped hydro storage tested at the beginning of 2026, amid the most severe heatwave in years.

Temperatures above 40C posed “challenges” to storage technologies, reported Energy Storage News, which explained that their output and operating times were reduced by the increased need for their cooling systems to operate.

Despite these challenges, the use of battery storage is helping to spread the ability of renewables to meet electricity demand during heatwaves. For example, a combination of solar and battery energy storage “kept the lights on” in California amid a heatwave in 2024.

By storing abundant power during the day, it can be discharged during evening peaks, helping to minimise generation constraints and thereby keep power prices down.

Dr Rosslowe says:

“The extreme price spikes that we witness during heatwaves are a blaring signal for more power system flexibility. That could come from battery storage, demand response, or increased interconnection between countries or regions.”

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The post Factcheck: How nuclear, gas, wind and solar power are affected during heatwaves appeared first on Carbon Brief.

Factcheck: How nuclear, gas, wind and solar power are affected during heatwaves