Solar power generation in the UK reached a new record over the summer of 2026, as temperatures across the nation soared, according to new analysis by Carbon Brief.
Collectively over June, July and August, solar farms and rooftops generated 8.8 terawatt-hours (TWh) of electricity in the UK*, as shown in the chart below.
Speaking to Carbon Brief, Chris Hewett, chief executive of trade association Solar Energy UK welcomed the new record, adding that it was driven by “clear skies and continued growth in deployment”.
This surge in generation took place amid the hottest summer on record in the UK, with five heatwaves between May and August.
Summer 2026 was the sixth sunniest on record, with more than 620 hours of sunshine, according to the Met Office. England and Wales – which experienced the most extreme heat – saw their second-sunniest summers on record.
June 2026 was the hottest June in England since records began in 1884, according to Met Office data, while Wales and the UK as a whole experienced their second-warmest June.
It was the driest July for England and Wales since records began in 1836, with some parts of London seeing no rain at all in the month, while Wisley in Surrey had no rain for 62 days.
In England, temperatures peaked at 38.1C at Kew Gardens in London on 13 August.
According to the Met Office, this summer’s record mean temperature was made 130 times more likely by climate change.
Amid these hot and sunny months, solar power generation increased 23% from the same period in 2025. This is double the level of solar generation over the summer of 2021, according to Carbon Brief analysis.
While solar panels can be affected by periods of extreme heat, the longer hours of daylight and higher levels of irradiation over the summer more than offset any efficiency losses.
June, July and August all saw solar set new monthly records for solar generation – July saw the highest solar generation in a calendar month ever, with 3.3TWh meeting 15% of overall electricity demand for the month.
As of the end of August, the total UK solar generation in 2026 stood at 17TWh – 13% higher than the same point in 2025.
The number of solar farms and rooftop installations has grown substantially in recent years, helping to boost generation. Domestic rooftop solar accounts for around 29% of total capacity.
In 2025, the UK’s solar capacity reached 21 gigawatts (GW) by the third quarter of the year, according to UK government figures. This is a jump of 3GW, or 18%, year-on-year, as Carbon Brief reported in January.
(Capacity is the maximum output possible from an electricity generation, whereas generation is what was produced over a certain time period, such as a day, month or year.)
This includes nearly 172,000 solar installations that have been fitted across the UK since the start of 2026, according to recent government figures. In July alone, more than 19,800 rooftop solar panels were installed – the equivalent of one installation every two minutes.
In total, nearly 1.7m households in the UK now have solar panels installed.
Over 26 heatwave days this summer – periods of at least three days when temperatures exceed the Met Office’s county-level heatwave temperature threshold – UK households with rooftop solar panels avoided an estimated £86.7m in electricity costs, according to analysis by Utility Bidder.
Talking about the surge in solar generation this summer, Hewett says:
“[It] not only kept bills down for people with solar and batteries in their homes, but helped keep overall power prices much lower than they would have been if Britain had been relying on more gas generation during the day”.
Despite the record generation, no new half-hourly solar power output record was set in the summer of 2026. This still stands at 15.2 megawatts (MW) on 23 April 2026.
* This article refers to the UK throughout, but strictly relates to the island of Great Britain, made up of England, Scotland and Wales. Northern Ireland is part of the separate, all-Ireland electricity system.
Conservative shadow energy secretary Claire Coutinho during a press conference on 19 August 2026. Credit: Stefan Rousseau / Alamy Stock Photo
The report ‘grossly simplifies’ long-duration energy storage
In a new report, the opposition Conservatives argue that UK electricity prices are too high and that it would be better for the climate to have cheap electricity, even if that means using more gas.
The idea is that cheap power would encourage people to use more electric vehicles (EVs) and heat pumps, leading to higher electrification of the economy and lower emissions.
This is at the heart of a Conservative push to abandon the UK’s net-zero by 2050 target and various climate policies, which the party says are “bankrupting” the country.
Now, the party is using a report by centre-right thinktank Onward to advance this argument, claiming that the UK could save “over £320bn” by scrapping net-zero policies.
In the report foreword, shadow energy secretary Claire Coutinho says this approach would make electrification “more attractive”, ensuring both “prosperity and a better environment”.
However, the report fails on these terms, as its alternative scenario ends up with less electrification of heat and transport and an extra 524m tonnes of carbon dioxide (MtCO2) emissions by 2050.
Moreover, the report relies on a series of questionable assumptions to claim that gas and nuclear will be cheaper than renewables – including the idea that gas prices will be low and stable.
Experts tell Carbon Brief that with credible assumptions, the report’s conclusions would be flipped on their head, such that renewables – not gas and nuclear – would bring the “lowest total costs”.
Iain Staffell, an associate professor of sustainable energy at Imperial College London, tells Carbon Brief that while the report “tells a good story”, the modelling underpinning it “has more holes than a Swiss cheese”.
In this factcheck, Carbon Brief speaks to experts and identifies flaws in the report, explaining why they undermine the anti-net-zero rhetoric of the Conservatives and their supporters.
The report by Onward is based on modelling by advisory firm Transira Energy, which compares two pathways out to 2050.
One is a “business-as-usual” scenario based on current “net-zero” policies. (Nevertheless, this only achieves a clean power system by 2045 – far short of the 2030 Labour target.)
The other is an “alternative policy pathway” (APP), developed by Onward, which assumes the UK’s 2050 economy-wide net-zero target is abandoned after the next election in 2029.
The latter says it places “greater emphasis on reducing the cost of electricity”, which includes fewer renewables, no electrification goals and more gas and nuclear power capacity.
This mirrors the policy platform set out by the Conservatives, who argue that “net-zero” drives up energy costs and that climate change can be tackled without such targets.
In fact, the Conservatives say their “common sense” approach would make it easier to cut emissions, as shadow energy secretary Claire Coutinho states in the report foreword:
“If we want those emissions to fall, then we need people to want to use electric cars and electric heating – then our priority should be to make electricity cheap.”
Yet, this argument is firmly contradicted by the report itself.
The APP results in an extra 524MtCO2 being emitted between 2030 and 2050 – equivalent to the annual emissions of South Africa.
The Transira Energy analysts say this is “explained by an increased share of unabated gas-fired capacity”.
Finally, it is worth noting that the UK’s net-zero target is based on the fact that the planet will continue warming until global emissions reach net-zero. Without such targets, climate change – and its impacts – will get worse.
The plan would slow electrification
Contrary to Conservative claims, uptake of heat pumps and electric vehicles is actually expected to be slower in the alternative scenario, “despite lower electricity costs”.
This is due to the removal of supportive government subsidies and mandates, such as the boiler upgrade scheme and the 2030 ban on the sale of new petrol and diesel cars.
Overall electricity consumption is 7% lower in the APP, compared to the current pathway.
“While this is an interesting scenario to explore, it overlooks potentially important feedback effects – mainly, as electricity prices and the capital costs of electrification technologies fall, uptake would be expected to increase.”
A related point was made in a LinkedIn post by Tara Singh, chief executive of trade body RenewableUK, who noted:
“APP makes the electricity system cheaper partly by electrifying Britain less – while leaving the fuel costs that replace electricity outside the model.”
For example, Singh estimates that the extra petrol and diesel fuel expenditure to replace the missing electric vehicles (EVs) on the road could be around £65-95bn over two decades. These costs are not included in the APP scenario.
The only sector that sees increased power demand is data centres, due to policy support to “prioritise” new grid connections for these facilities.
Quiroga notes that the costs of accelerating data centre connections “are not mentioned at all” in the report.
In short, the proposed pathway involves removing grants that help households buy EVs and heat pumps, while providing more policy support for the AI industry.
Finally, Onward stresses the UK’s “high spark gap” – referring to the electricity-to-gas price ratio. This makes switching from gas boilers to heat pumps less appealing for consumers, given the relatively high price of electricity, compared to gas.
However, Matt Elliott, lead economic analyst at the Energy and Climate Intelligence Unit (ECIU), says the analysis does not indicate this gap would substantially change in the proposed APP. He tells Carbon Brief:
“The report claims that electrification would happen even without specific policies, simply due to lower retail electricity prices driving consumer choice. However, its own modelling indicates that the gas-electricity price ratio would actually rise in the early years and end up only marginally lower than today by 2050.”
In other words, in the APP the price of electricity compared to gas would not fall sufficiently to drive consumers towards heat pumps without subsidies or other incentives.
Rather than scrapping net-zero policies, analysts have suggested shifting tax and policy levies from electricity to gas, or breaking the link between wholesale gas prices and electricity, as more effective ways to reduce the spark gap.
Gas prices are unlikely to remain low and stable
The “alternative” scenario pushed by the Conservatives continues to rely heavily on gas for both electricity generation and heating.
This includes constructing new gas power plants in a bid to lower electricity prices, despite the fact that gas is the main driver of high electricity prices in the UK.
In recent years, the largest spikes in energy prices have been triggered by wars in Ukraine and the Middle East, which have disrupted fossil-fuel supplies and sent gas prices spiralling.
(Indeed, the report was published on the same day the Office for National Statistics announced that inflation had jumped to its highest rate in four months, due to energy costs surging because of the impact of the Iran war on global oil and gas supply chains.)
Despite this, the scenario set out by Onward assumes that gas prices drop to pre-conflict levels and remain that way for the next two decades.
Ashutosh Padelkar, research lead at Aurora Energy Research, tells Carbon Brief that the gas price assumptions are “hard to fathom” and significantly at odds with future expectations, from both Aurora and other market analysts.
Analysis by E3G and ECIU in 2025 concluded that four years of energy spikes caused by the post-pandemic demand surge and Russia-Ukraine war had cost the UK £183bn.
The Onward report acknowledges that the new scenario is “more exposed to a future gas price shock” than the current net-zero scenario. It suggests that a new spike could increase fuel costs in the gas-reliant scenario by another £6bn in 2040.
However, Onward argues that the impact of gas price spikes on consumers would be “significantly smaller” than the shock following Russia’s invasion of Ukraine. This is owing to existing renewable energy contracts and future nuclear power construction in the APP.
In the press release accompanying the new report, Conservative leader Kemi Badenoch is clear that “our plan means using our own oil and gas in the North Sea”.
This mirrors rhetoric that has been widespread on the right of UK politics, stressing the importance of expanding North Sea drilling as a way to cut energy bills.
However, given the relatively small volumes remaining in the North Sea, the UK will likely remain reliant on gas imported from the US and the Middle East.
Gas prices will still be set globally and remain subject to geopolitical turmoil, no matter where the UK sources its supplies.
Given this, Johnny Gowdy, director of the thinktank Regen, tells Carbon Brief that the scenario presented by the Conservatives is “a call to rely on imported gas, with global gas prices”.
The plan assumes gas plants are cheap to build
The Conservative plan involves building new gas power plants, in order to meet part of the nation’s growing electricity demand without relying on renewables.
Onward states that the UK “has lost firm generation capacity” – such as gas and nuclear plants – and replaced it with “intermittent”, or variable, power in the form of wind and solar.
To remedy this, its alternative pathway involves building an extra 21 gigawatts (GW) of gas power plants by 2050 – equivalent to around 20 new facilities. This is roughly a 70% increase from the UK’s current capacity.
However, the small print in the accompanying Transira Energy report explains that it assumes capital expenditure – the cost of building the power plants – is £650 per kilowatt (kW).
This is considerably lower than other recent analyses, which tend to cite capital expenditure figures that are more than double this estimate.
For example, a 2025 GridLabreport notes that new US gas power plants set for completion in 2026 and 2027 had a cost range of $1,116/kW (£819/kW) to $1,427/kW (£1046kW).
However, it adds that more recent projects are “routinely reporting” costs of $2,000/kW (£1467/kW) or more. Other sources have reported up to $2,800/kW (£2054/kW).
Gas power plant costs have increased significantly in recent years – a trend that has been attributed to a tight supply of gas turbines worldwide.
This, in turn, is the result of increased demand for gas turbines to power data centres and countries transitioning from coal to gas.
The International Energy Agency (IEA) says data-centre demand in the US is “limiting the availability of turbines for near-term deployment elsewhere in the world”.
Nuclear faces high costs and delivery challenges
The Onward report champions a substantial increase in nuclear power capacity.
However, it fails to explain how this could be facilitated or why its cost assumptions are lower than the most recent nuclear projects in the UK.
Within the report’s net-zero scenario, there is 13.3GW of nuclear power by 2050, roughly double the current capacity. It notes that this will be financed under the regulated asset base (RAB) model – a government-backed funding approach announced in 2022.
Under the APP scenario, nuclear power capacity more than triples from current levels to 20GW by the middle of the century, all backed by the RAB model.
The report adds:
“Reducing nuclear construction costs and timelines becomes the core energy priority of the UK government, with measures to improve the availability of sites and grid connections.”
The report acknowledges that the APP scenario “faces significant cost headwinds from expensive nuclear capacity”.
However, it suggests that large-scale nuclear power stations built in the 2040s could cost £122-£138 per megawatt hour (MWh) in 2025 terms.
Hinkley Point C – which in 2018 became the first new nuclear power plant to begin construction in the UK since the 1980s – has a “strike price” of £138/MWh for 2030. (This is the fixed price for the electricity it will generate, guaranteed by the power plant’s contracts for difference agreement.)
This price is at the top end of Onward’s forecast range for “levelised cost of electricity” (LCOE) – the average total cost of building and operating an asset over its lifetime.
Hinkley Point nuclear power station. Credit: Rory Hailes / Alamy Stock Photo
As such, the report suggests, on average, costs will fall over the course of the decade from 2030, but provides little detail as to how this would happen.
As Richard Howard, global research director at Aurora, wrote on LinkedIn, the cost assumptions for nuclear are “optimistic”. He adds:
“It assumes that the LCOE of nuclear will fall 10-20% below the *original* cost of Hinkley Point C, when we know that nuclear costs escalated massively since the HPC deal was struck. The UK does not have a great track record of managing down the costs of nuclear.”
In fact, Sizewell C – a replica of Hinkley Point C in the early stages of construction in Suffolk, which received a final investment decision in 2025 – has a considerably higher strike price of £150/MWh in 2039.
Hinkley Point C is the first new nuclear power plant to be built in 30 years in the UK. It has been beset by delays and nearly doubled in cost since it was originally approved.
A footnote in the Transira Energy report adds that its calculations for the cost of nuclear include expected capital expenditure for new large-scale plants ranging from £10,000/kW to £12,500/kW.
While the 3.26GW Hinkley Point C was originally supposed to have a price tag of £18bn, which would equate to £5,521/kWh, costs have repeatedly increased. More recent estimates from developer EDF suggest a figure of £10,736/kW, closer to Onward’s figure.
However, if this is adjusted for inflation for 2026, this jumps closer to £14,724/kW.
As such, the upfront cost of new nuclear is already around £2,500 more per kilowatt than the assumptions in the report for 10 years from now.
The report provides limited information about how these costs would fall so substantially.
It suggests that the recommendations from the 2025 Fingleton review should be implemented in full to cut the cost of the technology.
The Fingleton report – a full review of the UK’s nuclear sector by the Nuclear Regulatory Taskforce, led by John Fingleton – found an “overly complex” and “bureaucratic” system was holding back the nuclear industry. It advocated for “smarter regulation”, as an overhaul of the planning regime.
In March 2026, the Labour government committed to full implementation of the Fingleton review by the end of 2027. Despite this, the Onward report includes the implementation of the Fingleton review in the APP scenario, but not the net-zero scenario.
The report’s high network cost estimates do not ‘add up’
The biggest drop in costs outlined in the Onward APP scenario comes from a reduction in network costs, but experts have said that this “just doesn’t add up”.
Network costs are broadly made up of the price of building, maintaining and operating the transmission and distribution systems.
A reduction in network spending accounts for £137bn of the £320bn in “savings”, compared to the net-zero scenario that sees significant network expansion to help facilitate more renewables on the grid.
This drop is “thanks to a higher utilisation of firm power system with supply located closer to demand”, the report says.
In particular, the report points to discrepancy between the “best wind resources” being located in the north of Scotland, while the major centres of demand are in the southeast of England. As such, currently grid expansion is needed to avoid constraints or the requirement to curtail generation in windy periods with low demand.
By avoiding the connection of geographically dispersed generation assets, such as 78GW of generation, storage and interconnectors, the APP scenario can reduce total network costs by 43%, according to the report.
Staffell tells Carbon Brief that the £137bn saving has “a convincing story to it – if we build more fossil and nuclear capacity we can utilise the system better”.
However, he adds that Onward gives “so little detail about how this works that it’s hard to comment”.
The Transira Energy report notes that the APP still includes £19bn in investment for the electricity network, covering the cost to maintain the existing system and connect new gas and nuclear generation.
However, this 86% drop in new transmission investment compared to the BAU scenario leans on “flawed logic”, according to Tara Singh from RenewableUK.
On LinkedIn, she explained that it “rests on an extraordinarily aggressive assumption about how little grid Britain will need”, adding:
“Onward assumes £137bn of new transmission assets under BAU between 2030 and 2050, but only £19bn under their plan, even though by 2050 it still has 32m EVs/hybrids, more than 6m additional heat pumps, 45GW gas, 20GW nuclear and – particularly strikingly – 62 terawatt hour (TWh) a year of datacentre demand. Is this grid figure credible…?”
Beyond this, the report also attributes a significant portion of the proposed savings to cuts in “balancing costs”. These are the costs to the system operator of balancing electricity supply and demand.
It claims that having more firm generation located closer to demand and existing transmission infrastructure will “save billions of expenditure on network expansion and balancing costs”.
Onward suggests that under the APP scenario, the cost of keeping generation and demand balanced would fall by £67bn.
However, claiming savings by both cutting network expansion and balancing costs amounts to “double counting” and “just doesn’t add up”, according to Aurora’s Padelkar.
He tells Carbon Brief that including both high capital expenditure for the electricity network and high balancing costs in the BAU scenario is “difficult to reconcile”.
Expanding the electricity network would reduce constraints, reducing the need for constraint management. Such a move would lower balancing costs.
As noted by the National Energy System Operator (Neso), retaining the current transmission network into 2030, with no expansion, would mean constraint costs could reach around £12.7bn a year. But building new network capacity could cut costs by as much as 75%.
Padelkar says:
“They’re saying ‘we continue to invest in the network’…But somehow the network [balancing] costs just don’t come down…This is basically saying ‘we’re paying both to fix the problem and to have the problem’. You can have one of the two, but you can’t have both.”
Despite the claim that the APP approach will lead to the cheapest electricity, Padelkar says that the report does not present a “consistent picture” as to how the system would operate, pointing to the approach to network and balancing costs. He adds:
“Overall, we would expect that once these figures are correctly accounted for, that renewable energy would remain the cheapest form of a form of decarbonisation. I would even further flip the argument around, to say that decarbonisation is not a prerogative [on] its own, but because it also achieves lowest total costs.”
The system integration costs are ‘far out of line with mainstream thinking’
A central argument in the Onward report is that the costs of renewables are higher than often claimed by proponents, due to the wider system costs of having a large amount of “intermittent” generation.
As such, it proposes pulling back support for wind and solar, and instead putting focus on “firm generation” sources, particularly gas and nuclear power.
This relies heavily on the claim that “system integration costs” for wind and solar are much higher than is being “properly revealed” in either contracts for difference (CfD) auctions or levelised costs estimates.
(CfD’s are power contracts between generators and the government, which work as the UK’s main method for supporting the development of renewables by providing long-term price certainty to developers.)
Therefore, when assessing the overall cost of renewable energy, the cumulative network investment, balancing and ancillary services system costs necessary to manage such variable generation must be considered, it suggests.
The existence of integration costs is not widely understood, but the scale of their impact is disputed.
The report continues that if these costs are taken into account, the “marginal system integration costs” of renewables are “much higher than their individual levelised costs”.
Onward suggests that the cost to integrate additional offshore wind, onshore wind and solar onto the electricity system is £125/MWh. This is far higher than the cost of generating electricity from these sources in the first place.
The figure has been challenged by a number of commentators, with Staffell telling Carbon Brief that this is “very far out of line with mainstream thinking”.
Analysis published in Nature suggests that if 80% of the electricity mix comes from renewables, the system integration cost is around €30/MWh (£26/MWh).
Elsewhere, engineering firm Afry put the total cost of electricity at around £55-75/MWh in a high-renewable system. This is “less than [Onward’s] integration cost alone”, Staffell adds.
The high price tag of the £128/MWh marginal integration “is derived by apportioning additional balancing and transmission costs solely to 60GW of new wind and solar deployed from 2030 onwards”, explains Callum MacIver, research fellow at the University of Strathclyde and the UK Energy Research Centre.
He adds:
“[This figure] only looks at the cost side and there is not enough published detail on where the renewables are deployed and the transmission upgrades it triggers to critique the scale of the numbers presented.
“It also excludes potential wider system benefits of further renewables deployment, including reduced wholesale prices, avoided fuel and carbon costs and reduced exposure to future external gas price shocks, which are properly examined by looking at overall system costs and testing various sensitivities including different gas price futures.”
Writing on LinkedIn, Adam Bell – a partner at consultancy Stonehaven – suggests that the £125/MWh system costs are “really egregious”. He explains:
“The ‘system costs’ of renewables…rests on assuming that all additional network upgrades and balancing costs for a net-zero system after 2029 are attributable to additional renewables deployed in that net-zero system.
“Many of those costs relate to existing renewables as well as nuclear, so this likely overstates system costs by an order of magnitude [roughly 10-fold].”
Furthermore, the system costs for the APP scenario are not fully accounted for in the report. Regardless of the technology mix, old network and generation assets will need replacing, adding additional costs to the system.
The proposed changes could undermine investor confidence
The APP scenario involves stripping back all support for renewables going forward.
It calls for the CfD scheme to end in 2030. Pre-existing CfD contracts would continue under APP, but after this decade, all further support would “exclusively” be for nuclear power.
Additionally, the renewable obligation (RO) payments for existing wind and solar would end from 2033. These are legacy contracts signed ahead of the scheme closing to new applicants in 2017. Payments are expected to continue until 2037.
(Onward makes an exception for the large-scale biomass power plant owned by Drax, which already has a contract with the UK government to switch from an RO to a low-carbon “dispatchable CfD”. This switch is included under both the net-zero and APP scenarios, in recognition of the “importance of its contribution to generation and to system stability”.)
Both the CfD and RO schemes have contributed significantly to the expansion of the renewable energy sector in the UK. For example, despite coming to an end in 2017, nearly 30% of current electricity supplies are still covered by RO contracts.
It is unclear from the report what the 10GW of capacity currently expected to receive the RO would do beyond 2033.
Writing on Bluesky, Tom Haddon, senior economist at Arup, says that if, as the APP scenario proposes, the UK “bin[s the] RO”, this could force 10GW of renewable capacity still on the system to simply shut down after 2033.
Such a dramatic change to a longstanding support system could have an impact on investor confidence.
Padelkar tells Carbon Brief that energy investors are often involved in numerous technologies. He adds:
“You wouldn’t be able to say ‘yeah, not going to continue honouring this contract [for renewables], but I expect you to sign this new one for me [to build new nuclear]’. That just wouldn’t work.”
As such, there is no guarantee that investors would agree to enter into government-backed RAB contracts to develop nuclear power plants, having just seen government-backed RO contracts being reneged on four years early.
Carbon market ‘savings’ are ‘just rearranging things on a spreadsheet’
One of the large chunks of “savings” identified to bring down electricity prices in the Onward report is £94bn from “lower wholesale prices, thanks to the removal of carbon taxes”.
Onward argues that this reduces the cost of gas power plants, which frequently set wholesale power prices under the marginal pricing system.
Staffell tells Carbon Brief that this is a “concern” when considering the report’s findings:
“That is £94bn no longer going into the government coffers, so it’s not saving the country any money; it’s just rearranging things on a spreadsheet. This lowers electricity bills, but does that get compensated for by higher taxes elsewhere, or do we have to take on a larger national deficit, or does it go hand-in-hand with cutting public services?”
Tom Edwards, a consultant at Cornwall Insight, wrote on Bluesky that it would be “madness” to simply remove the UK ETS and “expect things to remain stable”.
The UK currently sources around a tenth of its electricity via interconnectors that link its grid up with Ireland and parts of mainland Europe. It also exports electricity to other European countries when it has surplus supply.
These relationships would be complicated if the UK abandoned its carbon price on electricity altogether.
Alongside ending support for renewables, the new Onward scenario also removes subsidies for new interconnectors, although it says “existing interconnectors will continue”.
The Transira Energy analysis says there would be “new cross-border trading arrangements” from 2031. Such “arrangements” would, presumably, need to be negotiated from scratch with the EU.
Specifically, the report proposes a “carbon reference price” for electricity sold to the EU to “prevent carbon leakage and the distortion of cross-border electricity flows”.
Adam Berman, policy director at Energy UK, pointed out that the post-Brexit trade and cooperation agreement between the UK and the EU includes a legal commitment by the UK to maintain a carbon price on electricity. He wrote that the Onward proposal “would run contrary to that agreement”.
The report ‘grossly simplifies’ long-duration energy storage
The Onward report states that it would cancel support for long-duration energy storage (LDES), such as large batteries and pumped hydropower.
This follows the government recently launching a “cap-and-floor scheme” to support the technology. In June 2026, the nation’s energy regulator Ofgem identified 16 LDES that it is “minded to” support under the new scheme.
LDES can store power across days, weeks or even seasons, helping to boost electricity system security. Analysis by analytics company LCP Delta suggests that rolling out LDES technologies could cut energy system costs in the UK by more than £24bn between 2030 and 2050.
Onward lists support for storage systems – including LDES, as well as smaller batteries, which are only briefly mentioned in the report – as one of the “costs of an intermittent-first, low-carbon electricity system”.
The report suggests that even if all 16 of the projects shortlisted by Ofgem were built, the total would only provide around five and a half hours of generation.
It adds: “This is not enough to make it through a winter spell of low wind and sun”.
This assertion is based on the total storage capacity of all the projects being 136GWh.
However, the report “grossly simplifies the operation of LDES”, explains Padelkar. He adds:
“This assumes a rate of discharge that the fleet doesn’t have. Further, this LDES capacity would play a key role in reducing the balancing and ancillary costs, even in the early 2030s, by helping absorb cheap wind generation in Scotland in constrained periods and then discharging it when the transmission from Scotland to the south of Great Britain is not constrained.”
The role of LDES is more complex than simply all projects providing the entire electricity demand for the nation in one go. The projects are designed to act together with other assets to absorb excess supply, smooth out peaks in demand and step in to provide cheaper power when prices spike.
Related
Q&A: What is ‘long-duration energy storage’ – and why does the UK need it?
As successive heatwaves hit Europe, air-conditioning (AC) has emerged as a new front in the international “culture war” over climate action.
France, Germany and the UK have experienced record-breaking heat and thousands of heat-related deaths this summer, with June temperatures in many regions passing 40C.
This has drawn attention to the relatively low rates of AC use in these countries – and in Europe as a whole – especially when compared to its widespread adoption in the US.
Right-wing politicians, including National Rally in France and the UK Conservatives, have styled themselves as champions of AC, while opposing efforts to tackle climate change.
Missing from most of these interventions is the fact that human-caused climate change has made once-rare heat far more common, in what is the world’s fastest warming continent.
Carbon Brief analysis for this article shows that, until the 2020s, it was rare for many European cities to see days above 30C, making AC an unnecessary expense.
Here, Carbon Brief explains – via eight facts – why AC rates in some parts of Europe are relatively low, as well as clarifies and contextualises some of the misleading claims circulating about the technology.
AC installation rates in northern parts of Europe are very low. The best available estimates suggest that 6% of households in Germany and just 4% in England use AC.
However, these rates are largely explained by the historical climates in these nations.
Unlike the US, much of the housing stock and infrastructure in Europe was built at a time when AC did not exist and was not necessary.
Moreover, nations such as France, Germany and the UK have only started to regularly experience extreme heat in recent decades.
The chart below shows the average number of days per year, in each decade since the 1950s, when maximum temperatures have exceeded 30C in major European cities. Capitals such as London and Paris have seen a significant jump since around 2000.
Average number of days per year with a daily maximum temperature of at least 30C in a selection of major European cities, for each decade since the 1950s. Source: Copernicus ERA5, Carbon Brief analysis by Dr Zeke Hausfather.
“For most of the 20th century, northern Europe simply didn’t need cooling. Homes in Britain and Germany were built to keep heat in, not out, because winters were cold and summers rarely hot.”
However, Rosenow says people’s views on AC in these countries likely stem from their historically colder climates. He adds:
“Attitudes formed around those facts, not the other way round…There is a cultural element, but it is the product of climate, not of some green ideological project.”
In the past, many in Europe relied on traditional methods to keep buildings cool. Richard Black, head of communications at Climate Analytics, made this point in a post on LinkedIn:
“Once, residents of cities such as Paris could cope with summer heatwaves by opening shutters and windows during the night, and closing them again in the morning to trap the cool air inside…We’ve reached a limit to this sort of adaptation.”
Now, with Europe around 2.5C warmer than pre-industrial levels, climate change is routinely driving record-breaking heatwaves, even in the north of the continent.
This is forcing a reappraisal of societies that were “built for a climate that no longer exists”, as the UK’s Climate Change Committee (CCC) put it in a recent report.
Experts broadlyagree that much of Europe will indeed need more AC, particularly in spaces housing the most vulnerable populations, such as care homes, schools and hospitals.
AC is already widely used in hotter parts of Europe
During periods of extreme heat, articles criticising “European hostility” towards the technology frequently note that “only about 20%” of households in Europe have AC.
Often, this is contrasted with the US, where more than 90% of households have AC installed. (In fact, the US is something of a global outlier, matched only by Japan.)
However, the continent-wide figure for Europe obscures the reality. In southern Europe – where temperatures are and have always been higher – AC is relatively common.
The map below, based on official EU data, shows that southern European nations use far more household energy for “space cooling” than those in the north.
Percentage share of household energy consumption used for “space cooling”, including AC, in EU member states and the Balkans. Source: Eurostat.
Government figures show that nearly 60% of Italian households have AC. Household-level data in many countries is patchy, but various analyses have placed that figure at 70-80% in Greece and 41% in Spain – with higher penetration in the hotter, southern part of the country.
The same pattern can be seen within France. International coverage has stressed the country’s “cultural resistance to AC”, citing a nationwide figure from 2020 that suggests “only” 25% of French households have AC.
However, polling data from customers of the Hello Watt energy app suggests that there is a distinct north-south divide in French uptake. At least 60% of households in Mediterranean regions of France are equipped with AC, according to these figures.
This can be seen in the map below, with households across northern regions, including Paris, reporting far lower AC installation rates, often below 5%.
Percentage share of households equipped with AC in departments of mainland France, according to polling data. Source: Hello Watt.
Finally, when making such comparisons to Europe, it is worth noting that high rates of AC use reported for the entire US also obscure significant differences between – and within – US states. This, too, aligns with differences in regional climate.
Hotter states in the US south have near-universal AC access. But in Washington, a north-western state with a climate more comparable to that of western Europe, 66% of people have AC in their homes.
Some European nations have ‘resisted’ AC – but its popularity is growing
International commentators have written extensively about Europe’s “longstanding resistance to cooling technology”, especially when compared to the US.
Often, European attitudes are attributed to “guilt” about AC’s energy demand, “cultural conservatism” or “overbearing governments”. One commentator ascribed divergent attitudes in Europe and the US to “different ideas about physical suffering and sacrifice”.
Meanwhile, right-leaning commentators and climate-sceptic groups have blamed “climate policies, which view AC as an unnecessary luxury”.
In general, these critiques often fail to consider the most obvious explanation, which is that AC adoption is low in northern Europe because the historical climate made AC unnecessary.
Critical articles have instead drawn attention to restrictions on AC use in some European countries, as well as the lack of support for AC in official heatwave guidance.
For France, in particular, polling has indeed highlighted widespreaddisapproval of AC, both on environmental grounds and due to alleged health impacts. Such messages have also been voiced regularly in French media and by left-leaning and green politicians.
However, across Europe there are plenty of signs that such attitudes are shifting, following successive spells of extreme heat.
Amid the June heatwave, there were reports from Germany, France and the UK of “skyrocketing” AC sales. This surge was even acknowledged by the foreign ministry in China, due to the nation’s role in supplying many of these products.
The shift is taking place in politics as well. Marine Tondelier, leader of the French Green party – which has traditionally opposed AC – recently stated that “there are places where we just can’t do without AC anymore”.
Overall, AC has been on the rise across Europe, with France, Spain and the Netherlands all using more than twice as much energy for AC and other “space cooling” technologies in 2024 as they did in 2015.
AC production in Germany has also risen by at least 75% in recent years and a growing share of German homes are being built with it installed.
Notably, there is little evidence that “climate policies” are blocking Europeans from installing AC. Polling in Germany shows that, while people are concerned about environmental impacts, the high costs of installing and running it are perceived as greater barriers.
Finally, there is an important distinction between individual AC units in people’s homes and installing them in public spaces, such as hospitals, care homes and schools.
While neither is widespread in France, support for the latter can increasingly be found across the political spectrum, from Greens to the far-right National Rally (RN).
AC emissions are growing, but its climate impact could be limited
Somepeople have noted that a wider rollout of AC in Europe could drive up emissions.
As noted in the Financial Times by columnist and chief data reporter John Burn-Murdoch, there is a logic to this argument, “at least superficially”. He writes:
“AC uses a lot of energy; if the proposed defence against emissions-driven global warming means emitting more, then we have an obvious problem.”
The emissions impact of AC depends heavily on the generation mix of a country’s power sector.
As such, it was responsible for 1bn tonnes of carbon dioxide (CO2) from electricity use globally. This equates to around 2.7% of total CO2 emissions globally from fossil fuels and industry.
(As well as indirect emissions through power use, AC units can also directly release greenhouse gases – used as AC refrigerants – when they leak or are improperly disposed of. Following the 2016 Kigali Amendment, countries are progressively trying to phase down the use of potent greenhouse gases in AC units.)
“There is a lot of alarmist messaging about how much electricity AC uses. However, on an annual basis, the demand is not that substantial. Currently, AC uses about 1% of electricity in the EU and catching up to adoption rates in the US would double this.”
According to the IEA estimates from 2018, “if left unchecked, energy demand from AC will more than triple by 2050”, reaching 6,200TWh of power.
By mid-century, households would contribute the most to the increase (70%), with at least two-thirds of the world’s households potentially having AC, according to the Paris-based agency.
Decarbonising electricity grids and energy-efficiency improvements can reduce AC emissions and their impact on climate.
For instance, in countries with a low-carbon electricity mix – such as France, where nuclear energy accounts for 67% of its electricity generation – expanding AC would have a more limited climate impact than in other countries.
In countries such as India, there could be a more significant increase in emissions as AC is adopted, due to the role coal plays in the country’s energy mix, especially during the night. Demand is growing fast – following low access historically – and many AC units are inefficient, with high electricity use.
According to a new working paper from the India Energy and Climate Center (IECC) at the University of California, Berkeley, “room AC” – portable plug-in units, as opposed to those permanently installed in buildings – already accounts for nearly one-quarter of India’s peak electricity demand (60-70GW) – and this is before the majority of Indian households have bought their first AC unit.
Dr Nikit Abhyankar, co-faculty director of the IECC, tells Carbon Brief that, as AC use is expanded across the world, it should be paired with solar and battery storage, where the “economics have completely shifted” in the last few years. This will help to cut both energy bills and emissions.
According to the IEA, accelerating energy efficiency improvements could deliver more than one-third of all CO2 emission reductions between now and 2030.
The global energy demand needed to run ACs alone in 2050 could be reduced by 1,300GW – the equivalent of all of China and India’s coal plants – through energy efficiency measures, it estimates.
Aditya Valiathan Pillai, a climate adaptation researcher at King’s College London, tells Carbon Brief that, as the use of AC expands, there is a conversation to be had about where and “what type of technology [is used] and who gets access” to it.
A final point is that many AC units are air-to-air heat pumps, which can efficiently heat homes, as well as keeping them cool. As such, wider AC adoption could boost the adoption of electrified heat, helping to cut emissions from gas boilers.
But AC also has a localised impact. It works by removing heat from indoor air and pushing it outdoors, raising temperatures on the street and exacerbating the “urban heat island” effect.
Left-leaning French politicians are among those citing this as an argument against AC, particularly in cities. Indeed, Emmanuel Grégoire, the Socialist mayor of Paris, appeared to be making this point in an interview with Le Monde, during the June heatwave:
“[AC] can be useful for cooling collective spaces and protecting the most vulnerable populations, but individual AC is a scourge – it makes the problem worse by heating the city even more.”
One study concludes that, in a city such as Phoenix, Arizona, where the technology is widespread, AC use during a heatwave can raise night-time temperatures by 1-1.5C.
Another models a nine-day heatwave in Paris – in a future with “massive” AC use – and finds an increase in external temperature of more than 2C, due to heat emitted by the units.
Given this, some scientists argue that AC can be a form of climate “maladaptation” – referring to actions that backfire and make people more vulnerable to global warming.
“AC may constitute a maladaptation because of its high demands on energy and associated heat emissions, especially in high-density cities.”
Compared to the US, more people in Europe live in dense, urban areas. According to Dr Vincent Viguié, a climate change economist at École des Ponts ParisTech, this could leave Europeans more exposed to heat from AC units. He tells Carbon Brief:
“If you live in a neighbourhood that is not dense, like in a suburban neighbourhood or in the countryside, you don’t care about this…So, once again, there is a key difference between US and European cities.”
Viguié is among the experts arguing that other climate-adaptation measures should be considered alongside AC, to keep entire cities cool – not just individual homes. He says:
“It’s not to say that the heat released by AC by itself is a reason to forbid AC…It’s just that not taking that into account may lead to bad decisions.”
The heatwave in June 2026 is estimated to have killed more than 20,000 people in Europe. In France – which has seen some of the hottest temperatures – the heatwave caused more than 2,700 heat-related deaths, according to analysis published by Carbon Brief.
AC does help to protect people from the effects of extreme heat. A 2021 study found that globally, AC averted an estimated 190,000 heat-related deaths annually during 2019-21.
With its much higher penetration of AC, the US has fewer deaths due to extreme heat than Europe.
Heat kills around 11 people out of every 100,000 in Europe, compared to around two people in the US, according to analysis by data scientist Dr Hannah Ritchie from Our World in Data.
Several publications have pointed out that “Europe’s heatwaves are deadlier than American gun violence”. While this is technically accurate in absolute terms, Ritchie says the comparison is “a bit silly” for a number of reasons, not least because on a per-capita basis, US gun deaths are higher.
Average annual deaths per 100,000 for heat and gun deaths in the US (red) and Europe (blue) to as close to the end of 2024 as possible. Heat deaths are based on excess death methodology, not death certificates. Source: By the Numbers.
However, experts suggest that AC is only one part of a wider effort to protect people from extreme heat.
A 2020 study looking at heat-related mortality in Canada, Japan, Spain and the US, found that excess deaths due to heat decreased between 1972 and 2009.
For example, the proportion of deaths due to extreme heat fell from 1.7% to 0.5% over the period in the US and 3.5% to 2.8% in Spain.
However, an increase in AC only explained 16.7% of the drop in the US and 14.3% in Spain.
The research concludes that “other factors have played an equal or more important role in increasing the resilience of populations”. This is supported by research that shows changes to cities, such as planting more trees, as well as behavioural shifts and public-health measures, can all protect people from dangerous heat.
Additionally, across Europe there is already a range of policies and measures in place to protect the most vulnerable from heatwaves. Many of these were brought in following the unprecedented summer of 2003, when 70,000 died from extreme heat.
These policies were highlighted by French environment minister Agnès Pannier-Runacher, in response to the far-right National Rally (RN) party’s AC proposals:
“The incompetent RN has just found out that nursing homes need air-conditioned rooms. Thank you, but it’s actually been mandatory since 2004.”
Another study found that measures that have already been rolled out in France would cut the projected death toll of a 2003-like heatwave by more than 75%. This is in part due to the expansion of AC in places such as nursing homes, but also other approaches, such as heat action plans.
For example, France has a multi-tiered action plan, which includes local governments ensuring access to cooled spaces and water, keeping a list of vulnerable individuals for targeted interventions, as well as national information campaigns.
‘Net-zero rules’ are not blocking AC installation in the UK
In the UK, Conservative politicians and right-leaning media have tried to pit the adoption of AC against net-zero policy.
Writing in the climate-sceptic Daily Telegraph, columnist Matthew Lynn claimed falsely:
“Strict net-zero rules now mean that aircon is effectively banned in the UK.”
(Further down the article, he concedes: “AC is not strictly speaking banned in new-build homes in the UK. But tough environmental rules mean that it is very hard, and expensive, to install in practice.”)
The same narrative has been used in articles by GB News, the Sun and others. A separate article in the Daily Telegraph’s “money” section goes further, claiming that AC had been “torn from homes under net-zero clampdown”.
A blog post from the Ministry of Housing, Communities and Local Government rebuts these claims, stating:
“There has been media coverage this week suggesting that AC is banned in homes. This is incorrect.”
For the UK, while it is true that fewer than 5% of homes currently have AC, this is largely due to the fact that it was not hot enough in the past to warrant the expense. Historically, the focus has therefore been on keeping buildings warm, rather than cool.
Current regulations do not ban the installation of AC outright. However – as the government’s blog post notes – there is no blanket rule, meaning there are some localised differences.
Certain areas – or certain kinds of properties – may be subject to additional complications for installing AC.
In a 2025 video on Instagram, shadow secretary of state for energy security and net-zero Claire Coutinho referenced the London plan, for example, which is a framework for development in the capital launched in 2021. She said:
“[London mayor] Sadiq Khan says no. The London plan says we shouldn’t have air con because it uses too much energy. But this is mad! This is a poverty mindset that we need to get away from.”
The London Plan does not stop homes from having AC. It simply says that, for new buildings, passive design measures should be prioritised, such as the orientation of the building, the window design and incorporation of measures such as external shading and trees.
A recent response from the mayor added further measures, such as the need to “minimise the necessity for the operation of mechanical measures including AC, which would further add to the heat island effect within urban areas and add operational cost to residents”.
Elsewhere, new-build homes across England must meet the requirements of “part O” of the 2022 building regulation updates. This includes addressing overheating in buildings through energy-efficient design and prioritising passive cooling, with AC as a last resort.
For existing buildings, most AC units fall under “permitted development rights”, meaning no planning application is required to install them.
Additionally, regulations were relaxed in 2025 to make it easier to install an air-to-air heat pump – which can both heat and cool air – without planning permission.
This means that, far from blocking the expansion of AC, net-zero policy has made it easier to install specific cooling systems.
Speaking to Carbon Brief, Andrew Sissons, director of sustainable future at Nesta, says the government must now implement its announced £2,500 subsidy for air-to-air heat pumps “as quickly as possible”, to further ensure that the technology can be rolled out efficiently. He adds:
“[The government] should also continue to expand permitted development rights for air-to-air heat pumps, with a particular focus on flats and homes in denser areas. As long as heat pumps meet the MCS [Microgeneration Certification Scheme] noise test, there are few reasons to limit their use via the planning system.”
Some properties, such as large homes, listed buildings or those in conservation areas, may still require planning permission to install an air-to-air heat pump or other AC. Sissons notes that this can add cost and delay to installation.
While it cannot be said that AC has been blocked or banned due to net-zero, neither has it been prioritised.
This may shift as temperatures continue to rise. UK government advisors at the Climate Change Committee (CCC) suggest that 22% of the UK’s housing stock will likely need active cooling, such as AC, to cope with 2C of global warming.
The CCC’s recent adaptation report also calls for all new homes to be built using low-cost, passive cooling measures, alongside more AC.
Active cooling such as AC is more likely to be needed for retrofitting existing homes, the report adds.
AC has become increasingly politicised in Europe, as demonstrated by France’s RN party announcing its “grand plan for AC” in all public buildings.
As noted by Dutch MEP Gerben-Jan Gerbrandy, this “far-right” embrace of AC is coming from the same people who for years have “delayed emissions reductions”.
In response, left-leaning policymakers in Europe have frequently downplayed the role of AC, prioritising programmes of urban greening and retrofitting older buildings.
Such approaches for dealing with extreme heat have already proved successful. Therefore, many experts argue that these methods, alongside AC, will be essential to prepare for a hotter world.
According to the IPCC’s sixth assessment report, adaptive infrastructure, such as urban forests and green roofs, can reduce energy use because of cooling, with co-benefits for climate, air quality, physical and mental health.
While retrofitting older buildings for heat as well as insulating them from the cold might prove challenging, urban greening and an active shade policy – one that determines how much of every street is exposed to direct sunlight – are simple measures cities can adopt.
Some experts have also warned about the high cost of running AC, expressing concerns that excessive reliance on the technology could increase energy poverty.
In a Carbon Brief guest post published in 2025, researchers at the Basque Centre for Climate Change found that framing AC as the “default solution” can miss the opportunity to design “more inclusive, human-centred responses” to rising temperatures.
William Lewis, a PhD candidate and one of the guest post’s authors, tells Carbon Brief it is not a case of “one or the other”, when considering AC and other options:
“We have this opportunity in European countries to choose a slightly different path [from the US], which isn’t AC in every single home.”
King’s College London’s Pillai says that, by centring the debate on AC, the far-right response to the heatwaves in Europe has “completely neglected the science of how you cool human beings”.
There are many solutions, he adds, that are already widely used across hot developing countries, such as ceiling fans, windows that open and cross-ventilation, as well as strategies to reduce cumulative hours of heat exposure.
Pillai tells Carbon Brief that, while places reaching 42C and higher “definitely need to think about AC very seriously”, places in the “low to mid 30Cs” could rely on these alternatives.
Behavioural change, he adds, is the “least glamorous part” of heat policy, but “pulls most of the weight” of protecting people. These include a wide range of actions and responses – from reducing heat exposure, to wearing lighter clothing and drinking more water and fluids.
There are also workplace protections. Pillai tells Carbon Brief that these could include legislation on mandatory work breaks, cooling and shade requirements at workplaces, as well as health insurance that covers heat stress days that have been lost by heat-exposed workers.
The UK avoided the need for gas imports worth £1bn in March 2026 thanks to record electricity generation from wind and solar, reveals Carbon Brief analysis.
Wind generation hit a new record for the month of March on the island of Great Britain, up 38% year-on-year, while solar nearly matched the output of last year’s exceptionally sunny spring.
Together, wind and solar generated 11 terawatt hours (TWh) of electricity in March 2026, up a combined 28% and setting a new record for the month, as shown in the figure below.
Monthly generation from wind and solar in terawatt hours on the island of Great Britain (England, Scotland and Wales), which has a separate electricity system from the island of Ireland, which includes Northern Ireland. Source: National Energy System Operator (NESO) and Carbon Brief analysis.
This record wind and solar output avoided the need to import 21TWh of gas – roughly 18 fully loaded tankers of liquified natural gas (LNG) – which would have cost around £1bn at current high prices due to the Iran war.
(This is based on gas costing 130p per therm, or £44 per megawatt hour, compared with the range of 120-170p per therm seen over the past month.)
At the same time, the record output from wind and solar saw electricity generation from gas falling 25% year-on-year in March 2026 to the lowest level ever recorded for the month.
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Emissions from the new data centres set to drive the UK’s AI “revolution” could be hundreds of times higher than government estimates, according to analysis by Carbon Brief.
There are dozens of data centres being developed across the country, potentially driving a surge in electricity demand.
Amid uncertainty about the scale and pace of this expansion, there are mounting concerns that new data centres could pose a threat to the nation’s climate goals.
UK government analysis concluded that the emissions from data centres would be negligible, even if they expand rapidly – a finding one campaigner tells Carbon Brief is “nonsense”.
In contrast, Carbon Brief analysis finds that emissions from powering data centres could be far higher than the government figures suggest, if at least a small amount of the electricity they need is generated by burning gas.
Data centres could run entirely on low-carbon electricity, but some in the sector have argued that the government’s AI ambitions require the UK to use more gas power.
If new data centres source a large amount of their power from gas, it could cause carbon dioxide (CO2) emissions equivalent to at least Denmark’s annual total.
‘AI superpower’
Data centres are energy-intensive computing facilities that are required to train and run complex AI models, among many other things.
The UK is one of the top-ranking nations for data-centre capacity, with roughly 1.8 gigawatts (GW) of facilities consuming more than 2% of national electricity. This could grow rapidly in the coming years as the government aims to make the UK an “AI superpower”.
Companies have already “achieved financial commitment” to invest in 71 new data centres that, if built, would require around 20GW of electricity, according to energy regulator Ofgem.
(For reference, the UK’s average electricity demand in 2025 stood at around 37GW.)
This potential increase in electricity demand has raised concerns from campaigners and some MPs about the impact of data centres on the UK’s climate targets.
Last year, the government’s plan for meeting its 2035 climate target noted that AI growth was “not factored into” emissions projections, although energy secretary Ed Miliband has said new data centres are captured in modelling of “overall electricity demand growth”.
The government is targeting a “clean power system” by 2030, with just a small amount of gas generation remaining. Extra demand from new data centres could require a rollout of clean power that is even faster than the growth already underway.
If clean-power growth does not keep pace, data centres could, therefore, prolong the use of gas power, either by requiring more gas to remain on the grid or by facilities building their own on-site gas generation.
There is significant uncertainty around future emissions from UK data centres, which will depend on the number of centres built, how clean their power is and when they come online.
The government published an analysis of its AI strategy’s climate impact last year, alongside a data-centre “roadmap”.
The analysis, released by the Department for Science, Innovation and Technology (DSIT) suggests emissions from future data centres will be minimal – reaching a maximum of 0.142m tonnes of CO2 (MtCO2) from 11.2GW of AI-related computing power by 2035.
(There is an additional 2.4GW of data-centre demand in this scenario that is not associated with AI, for which emissions are not calculated.)
This figure is based on what DSIT describes as a high-emissions, high-AI growth scenario. Yet it implies that each unit (kilowatt hour, kWh) of electricity supplied to the 11.2GW of AI data centres would be associated with less than 2g of CO2. In other words, their electricity supply would need to be almost completely decarbonised. The government aim is for 50gCO2/kWh by 2030.
In addition, the DSIT figure – for emissions associated with the entire UK data centre fleet in 2035 – is much lower than the emissions estimates reported in planning applications for individual UK data centres made by Google and other companies.
Gas power
The chart below, based on Carbon Brief analysis, shows how data-centre emissions could be far higher than the government’s figures suggest.
Even if gas-fired electricity only accounts for 5% of their supply – indicated by the smallest blue column below – emissions from 11.2GW of data centres would be around 2MtCO2. This is more than 10 times higher than the government’s top estimate for 2035.
If the same data centres rely more heavily on gas, emissions could be hundreds of times higher, exceeding 30MtCO2. This is roughly equivalent to the annual emissions of Denmark. Emissions could rise even higher if capacity increases in line with the extra 20GW of data-centre demand that Ofgem says is in the pipeline, as indicated by the red columns
Emissions from powering future UK data centres, MtCO2, under different scenarios. The UK government figure is based on a modelled estimate for total AI-related data-centre computing power in 2035. The blue bars combine the government capacity figure of 11.2GW with increasing shares of gas power. The red bars use the Ofgem estimate of 20GW of “mature” projects that may be built in the future, combined with existing capacity of 1.8GW, to reach a figure of 21.8GW. Source: DSIT, Carbon Brief analysis.
If data-centre expansion reaches 20GW and those centres rely heavily on gas power, then the figure could be as high as 70MtCO2, the annual emissions of Sweden. This would also be nearly 500 times higher than the government’s upper estimate, which it says is based on a “pessimistic decarbonisation” scenario.
(The numbers are not directly comparable as, unlike the AI-specific 11.2GW figure, it is unclear how much of this 20GW would be for AI, specifically.)
The government’s modelling states that AI emissions in 2035 would be “equivalent to below 0.05% of the UK’s projected total emissions”. It also says “this could be equivalent to the annual emissions of approximately 5,000 to 23,600 UK households”.
On the contrary, Carbon Brief’s analysis suggests data centres could, in fact, be equivalent to as much as 20% of the UK’s projected total emissions in 2035.
As for the number of households, Carbon Brief estimates that future data centres could result in emissions equivalent to as many as 11.4m homes, roughly a third of all UK households.
Dr Tim Squirrel, head of strategy at Foxglove – part of an NGO group calling for more government scrutiny of data-centre emissions – tells Carbon Brief the DSIT figures are “nonsense and threaten to derail our carbon budgets”. He says:
“The figures that DSIT projects here wildly downplay data-centre emissions, even by the standards of the most optimistic energy transition scenario. There is no way that the amount of compute they anticipate can be built and produce the miniscule emissions they’re calculating.”
In its analysis, the government attributes the low emissions figures to “more efficient models and hardware” and “the UK’s ambitious targets for electricity grid decarbonisation”.
When asked by Carbon Brief, DSIT declined to provide any more information about its analysis.
Clean growth
While the UK is prioritising data centres for AI, there is mounting industry pressure to allow gas-power expansion for this “critical” infrastructure, as is happening in, for example, the US and Ireland.
Developers in the UK have reportedly already “turned to gas” via private electricity supplies, due to struggles securing a connection to the public network.
Yet, new data centres could be completely emissions-free if they are powered entirely with on-site clean energy or using electricity from a decarbonised grid.
As it stands, most data centres are connected to the electricity grid. Some enter power purchase agreements (PPAs) in which they financially support renewable-energy operators, allowing them to describe their electricity as clean.
Katie Davies, head of energy and infrastructure policy at techUK, a trade association representing the technology sector, highlights this expansion of PPAs as important for driving the growth of wind and solar power:
“In doing so, data centres actively contribute to additionality by unlocking extra carbon-free capacity that might not otherwise come online.”
A report last year by Aurora Energy Research found that data centres could provide a “route-to-market” worth up to £35bn for 19GW of UK renewables. However, it added:
“If renewables capacity and networks don’t keep pace, additional data centre demand will likely be met by carbon-intensive sources of generation.”
The UK’s “AI opportunities action plan” includes the establishment of “AI growth zones“, which the government says will be in areas with “available clean energy”. It is also overhauling the grid connection queue, which Davies says is important:
“Reducing this queue through strategic alignment and the removal of speculative applications will be vital to ensuring [data-centre] operators do not have to turn to higher-carbon energy sources as a last resort.”
Responding to Carbon Brief’s analysis, a government spokesperson said:
“We want the UK to be at the forefront of AI, but we are clear this must be done sustainably. That is why our AI growth zones are supporting development in areas with access to clean power, while the AI Energy Council is exploring how AI can be powered by responsible, clean-energy sources.”
Update: After Carbon Brief contacted DSIT about this analysis, it deleted its emissions assessment and replaced it with text stating: “We keep analysis under routine review, and are updating this modelling to ensure it reflects the most up to date assumptions and analysis.”
Methodology
There is considerable uncertainty around data-centre power demand and emissions, with much of the relevant information not in the public domain. Carbon Brief has performed some rough calculations based on available data.
The government figure comes from an annex to DSIT’s UK compute roadmap. DSIT analyses the emissions impact of expanding the UK’s data-centre capacity to between 7.4GW in a “low compute-demand scenario” and 13.6GW in a “high compute-demand scenario” by 2035. (The majority of the demand in each scenario is from AI.)
DSIT also uses an “AI environmental impacts model” to estimate the greenhouse gas emissions from AI compute, only covering the 11.2GW AI component of data-centre capacity. It concludes that AI emissions in 2035 could range from 0.025MtCO2 to 0.142MtCO2. This includes both “direct” and “indirect” emissions, indicating that it covers more than just emissions from the electricity used to power the data centres.
A widelyreportedconsultation by the energy regulator, Ofgem, found that there are proposals for around 140 new data centres in the UK, which would require 50GW of electricity if they were all built.
In reality, it is highly unlikely that all of these data centres will be completed, with a “significant number” expected to fail when trying to secure funding or planning permission.
The 20GW figure used in this analysis is based on the 71 “mature” projects that have “achieved financial commitment with final investment decision”, according to Ofgem.
Carbon Brief used the top government figure of 0.142MtCO2, even though it represents a “pessimistic grid decarbonisation” and “high compute demand” scenario.
To calculate the emissions from powering data centres in the future, Carbon Brief assumes a data-centre “load factor” of 90%, which is in line with otheranalyses. The analysis uses different shares of gas in the centres’ power supplies to indicate a range of future possibilities, assuming emissions from gas power are 0.4MtCO2 per terawatt hour.
