Context: from decline to revival (in theory)
Nuclear power has been in retreat in the UK for two decades. The fleet of Advanced Gas-Cooled Reactors (AGRs) built in the 1970s and 1980s is ageing out, with most due to close by 2030. In 2020, the UK had 9 GW of nuclear capacity across 15 reactors; by January 2026, that has fallen to 5.9 GW across 9 reactors, as Hunterston B, Hinkley Point B, Dungeness B and Hartlepool closed. By 2030, only Sizewell B (1.2 GW) and the two Heysham plants (1.2 GW combined) will remain operational, leaving just 2.4 GW unless new capacity comes online.
This decline has been masked by the rise of renewables, but it creates a problem for net zero. Nuclear provides reliable, low-carbon baseload power that does not depend on wind or sun, making it a critical complement to renewables. Without it, the UK must rely more heavily on gas-fired power stations to provide backup when renewables are not generating, which increases emissions and exposes the grid to gas price volatility. The government's net zero strategy, published in 2021, assumes nuclear capacity will rise to 24 GW by 2050, providing around 25% of electricity. But getting there requires building new plants at a pace not seen since the 1980s.
The government has committed to a nuclear renaissance. The 2022 British Energy Security Strategy set a target of up to 24 GW of nuclear by 2050, including large plants like Hinkley Point C and Sizewell C, and a fleet of small modular reactors (SMRs). The 2023 Powering Up Britain plan reaffirmed this, describing nuclear as "essential" to energy security and net zero. But the reality is far behind the rhetoric. Hinkley Point C, the first new nuclear plant in a generation, is years late and billions over budget. Sizewell C is still seeking final investment approval. And SMRs, the great hope for a cheaper, faster nuclear future, remain unproven technology with no commercial deployment anywhere in the world.
The data: where nuclear stands in 2026
As of January 2026, the UK has 5.9 GW of operational nuclear capacity across 9 reactors at 5 sites: Sizewell B (1.2 GW), Torness (1.2 GW), Heysham 1 (1.2 GW), Heysham 2 (1.2 GW) and one unit at Hinkley Point B (0.5 GW, due to close in 2027). This is down from 9 GW in 2020 and 12 GW in 2010, reflecting the closure of ageing AGRs.
Nuclear generated 45 TWh of electricity in 2025, down from 55 TWh in 2023, providing 13% of total UK electricity generation. This is well below the 20-25% share nuclear held in the 1990s and 2000s. The capacity factor—the percentage of maximum output actually achieved—averaged 65% in 2025, down from 75% in 2020, as older reactors face more frequent outages for maintenance and safety inspections.
The pipeline of new nuclear is thin. Hinkley Point C (3.2 GW) is under construction in Somerset and is now expected to begin generating in 2029-2030, six years later than the original 2023-2025 target. Sizewell C (3.2 GW) in Suffolk received development consent in 2022 and is awaiting final investment approval, with construction expected to start in 2024-2025 and generation in the mid-2030s. Beyond these two, there are no confirmed projects, though the government has identified sites at Wylfa in Wales, Oldbury in Gloucestershire and Bradwell in Essex for potential future plants.
What's changing: Hinkley's troubles and the RAB gamble
Hinkley Point C: a cautionary tale
Hinkley Point C was supposed to herald the UK's nuclear revival. Announced in 2013 and approved in 2016, it was the first new nuclear plant since Sizewell B in 1995 and the first to use the French EPR reactor design in the UK. The project was structured as a Contract for Difference (CfD), guaranteeing EDF, the developer, a strike price of £92.50 per MWh (in 2012 prices, indexed to inflation) for 35 years—more than double the wholesale electricity price at the time.
The deal was controversial from the start. Critics argued it locked consumers into paying far above market rates for decades, subsidising French state-owned EDF and Chinese investors (China General Nuclear owns a 33% stake). Supporters countered that nuclear's high upfront costs and long construction times required revenue certainty, and that the strike price would look cheap if gas prices rose—which they did after 2021.
But the real problem has been delivery. Construction began in 2017 with a budget of £18 billion and a target completion date of 2025. By 2026, the budget has ballooned to £35-37 billion and the start date has slipped to 2029-2030, with EDF warning of further delays. The causes are familiar to anyone who has followed nuclear projects: design complexity, quality control failures, lack of experienced contractors, and supply chain disruption. The EPR design, while advanced, has proven fiendishly difficult to build. The only two EPRs completed globally—Taishan in China and Olkiluoto in Finland—were both years late and billions over budget.
Hinkley's delays have knock-on effects. The longer it takes, the more the UK relies on gas and imports to fill the gap left by closing nuclear plants. And the cost overruns undermine confidence in nuclear as a cost-effective route to net zero. At £35 billion for 3.2 GW, Hinkley costs roughly £11,000 per kW of capacity—far more than offshore wind (£2,500 per kW) or gas (£800 per kW). The electricity it generates will cost consumers around £110-120 per MWh (in 2026 prices), compared to £50-60 per MWh for new offshore wind.
Sizewell C and the RAB model
The government learned from Hinkley's financing debacle. Sizewell C, a near-identical 3.2 GW EPR project on the Suffolk coast, will use a different funding model: the Regulated Asset Base (RAB). Under RAB, consumers pay for the plant during construction through a levy on energy bills, rather than the developer borrowing upfront and recovering costs through electricity sales after completion. This lowers the cost of capital—because investors face less risk—and reduces the final electricity price by an estimated 30-40% compared to Hinkley's CfD model.
But RAB is controversial because it transfers risk from investors to consumers. Billpayers fund a plant that may be delayed, over budget or never completed, with no guarantee of lower electricity prices. The government estimates Sizewell C will add £15-20 per household per year to energy bills from 2026, rising to £40-50 by 2030 as construction ramps up. Critics call it a "nuclear tax" that forces consumers to subsidise a technology that may not deliver. Supporters argue it is the only way to make nuclear affordable and that the long-term benefits—low-carbon, reliable power for 60 years—justify the upfront cost.
Sizewell C received development consent in 2022, and the government took a 50% stake in the project in 2023, with EDF holding the other 50%. Final investment approval is expected in 2026, with construction starting shortly after and first power in the mid-2030s. If it proceeds, it will be the first nuclear plant built under RAB, setting a precedent for future projects.
Small modular reactors: the great hope
The third pillar of the government's nuclear strategy is small modular reactors (SMRs). These are smaller reactors—typically 300-470 MW compared to 1,600 MW for conventional plants—designed to be built in factories and assembled on site, promising lower costs, faster construction and greater flexibility. The UK government has invested heavily in SMR development, selecting Rolls-Royce SMR as the preferred technology in 2023 and committing £210 million in funding.
Rolls-Royce SMR claims it can build reactors for £2 billion each (compared to £11 billion for a conventional plant) and deploy the first unit by 2035. The modular design allows mass production, with costs falling as more units are built. The government's ambition is to deploy a fleet of SMRs across the UK, providing 10-15 GW of capacity by 2050 and creating a new export industry.
But SMRs are unproven. No SMR has been built at commercial scale anywhere in the world. Russia and China have deployed small reactors on ships and remote sites, but these are bespoke designs, not mass-produced modules. The US and Canada have SMR projects in development, but none are operational. Costs are uncertain—independent analysis by the National Infrastructure Commission suggests £3-4 billion per unit, not £2 billion—and there is no guarantee that factory production will deliver the promised savings.
Critics argue the UK is betting heavily on a technology that may not work, diverting resources from proven renewables. Supporters counter that SMRs offer a solution to nuclear's cost and construction problems, and that the UK's early investment will pay off if the technology succeeds.
What it means: can nuclear deliver?
The case for nuclear rests on three arguments: it provides reliable baseload power, it is low-carbon, and it enhances energy security by reducing reliance on gas and imports. All three are true, but they must be weighed against cost, construction risk and opportunity cost.
On cost, nuclear is expensive. Hinkley Point C will generate electricity at £110-120 per MWh, more than double the cost of new offshore wind. Sizewell C will be cheaper thanks to RAB financing, but still more expensive than renewables. SMRs may be cheaper still, but that is speculative. The government argues that nuclear's value lies in its reliability—it generates 24/7 regardless of weather—which justifies a premium. But critics point out that a mix of renewables, storage and flexible gas can provide the same reliability at lower cost.
On construction risk, nuclear's track record is poor. Every major nuclear project in the West in the past 20 years has been late and over budget. Hinkley is the latest example, but it is not unique: Flamanville in France, Vogtle in the US, and Olkiluoto in Finland all faced similar problems. The UK has not built a nuclear plant in 30 years, and the skills and supply chains needed have atrophied. Rebuilding them is possible, but it takes time and money.
On opportunity cost, the question is whether the £100 billion-plus the UK will spend on nuclear over the next 20 years (Hinkley, Sizewell, SMRs and future plants) could deliver more decarbonisation if spent on renewables, storage and grid upgrades. Modelling by Imperial College London suggests that a renewables-heavy system with storage and interconnectors can meet net zero targets at lower cost than a nuclear-heavy system, though it requires more land, more grid investment and greater public acceptance of wind farms and pylons.
What to watch next
Watch Sizewell C's final investment decision, expected in 2026. If it proceeds, it signals the government is committed to nuclear despite Hinkley's troubles. If it is delayed or scaled back, it suggests nuclear is losing political support. Watch Hinkley Point C's progress: if it starts generating in 2029 as planned, it will restore some confidence in nuclear delivery; if it slips further, it will deepen doubts.
Watch Rolls-Royce SMR's development. The company aims to submit its design for regulatory approval in 2026 and identify the first deployment site by 2027. If it hits these milestones, SMRs remain on track for a mid-2030s launch. If it faces delays or cost overruns, the SMR vision may unravel.
And watch the politics. Nuclear has cross-party support in principle, but the cost and delays are testing that consensus. If energy bills rise sharply due to RAB levies, or if Hinkley's final cost exceeds £40 billion, public and political support may erode. The UK's nuclear renaissance is still possible, but it is far from guaranteed. The next five years will determine whether nuclear is a cornerstone of net zero or a costly detour.
Frequently asked questions
Why is Hinkley Point C so late and so expensive?
Hinkley Point C uses a French EPR reactor design that has faced severe construction problems worldwide. The only two EPRs completed—Taishan in China and Olkiluoto in Finland—were both years late and billions over budget due to design complexity, quality control failures and lack of recent nuclear construction experience. Hinkley has suffered similar issues: welding defects, concrete quality problems, COVID delays and supply chain disruption. EDF, the developer, underestimated the difficulty of building a first-of-a-kind reactor in the UK after a 30-year gap in nuclear construction. The original budget was £18 billion in 2016; by 2026 it is £35-37 billion.
What is the Regulated Asset Base (RAB) model and why is it controversial?
RAB is a financing model where consumers pay for a nuclear plant during construction through a levy on energy bills, rather than the developer borrowing upfront and recovering costs through electricity sales after completion. This lowers the cost of capital (because investors face less risk) and reduces the final electricity price, but it means billpayers fund a plant that may be delayed, over budget or never completed. Sizewell C will use RAB, adding an estimated £15-20 per household per year to bills from 2026, rising to £40-50 by 2030. Critics call it a 'nuclear tax' that transfers risk from investors to consumers.
Are small modular reactors the future or hype?
SMRs are smaller nuclear reactors (typically 300-470 MW vs 1,600 MW for conventional plants) built in factories and assembled on site, promising lower costs, faster construction and greater flexibility. Rolls-Royce SMR has UK government backing and aims to deploy by 2035, but no SMR has been built at commercial scale anywhere in the world. Costs are uncertain—Rolls-Royce claims £2 billion per unit, but independent analysis suggests £3-4 billion. Until a first unit is built and operating, SMRs remain unproven technology, and critics argue the UK is betting heavily on a concept that may not deliver.