An accessible summary of the United Kingdom's current nuclear fleet, energy policy drivers and the roadmap for major projects such as Hinkley Point C, Sizewell C and Rolls-Royce SMR as the country aims for up to 24 GWe by 2050
The United Kingdom is reshaping its electricity mix with a renewed focus on nuclear power. Today the fleet that remains operational supplies about 5.9 GWe and roughly 15% of the nation’s electricity. Policymakers and industry actors are pursuing a combination of large reactors and smaller designs to reach an ambition of up to 24 GWe of new capacity by 2050.
The roadmap combines near-term construction projects, longer-term planning for projects awaiting final investment decisions, and a push to select and deploy small modular reactor technologies. Institutional changes and funding models are being adjusted alongside planning and licensing frameworks to make these investments feasible in a liberalised power market.
Current fleet and life-extension challenges
The United Kingdom operates nine reactors at five sites, comprised mainly of advanced gas-cooled reactors (AGRs) and one pressurized water reactor (PWR). Total operable capacity stands at approximately 5,883 MWe. Many of the AGRs have been granted multiple life extensions, but their original graphite-moderated designs are vulnerable to gradual cracking in the moderator graphite, a factor that constrains long-term operation.
Specific plant retirements are already scheduled: units at Hartlepool and the Heysham I complex are planned to close in 2028, while Heysham II and Torness are scheduled to cease operation around 2030. In contrast, the Sizewell B PWR is planned to run for 60 years, with operation planned through to 2055, subject to regulatory and technical approvals.
Projects under way and those moving toward decisions
Large-scale reactors
Construction of two European Pressurized Reactor (EPR) units at Hinkley Point C is under way, representing the first of the new large plants to reach advanced construction stages. A further pair of EPRs is proposed at Sizewell C. Government backing, including a major investment commitment announced in the 2026 spending review, cleared the path for a final investment decision process expected to conclude later in 2026 and subsequently resulted in a signed final investment decision for Sizewell C in July 2026.
Small modular reactors and technology selection
The government launched a selection process to identify which small modular reactor (SMR) design to back as part of the strategy to scale up nuclear capacity. In June 2026, Rolls-Royce SMR was named the preferred bidder, subject to final approvals. A site allocation was planned to follow in 2026, with the first grid connection of an SMR expected in the mid-2030s and a prospective final investment decision targeted for 2029.
Policy, markets and financing mechanisms
Energy policy in the UK has emphasised deep cuts in greenhouse gases over recent decades, anchored in the Climate Change Act and its legally binding carbon budgets. The government’s energy strategy after 2026 accelerated a drive for domestic power capacity and identified nuclear expansion as central to energy security and decarbonisation, with the explicit ambition of delivering up to 24 GWe by 2050 to supply around one quarter of national electricity.
To attract the large-scale capital required, the UK has used and adapted several support mechanisms. The Contracts for Difference (CfD) approach provides revenue stability for low-carbon generators by guaranteeing a strike price and settling differences with the market price. Other financing routes studied or applied include a regulated asset base model, government loan guarantees and direct state involvement. These instruments aim to de-risk projects and make nuclear investment compatible with a market-oriented power sector.
Institutional support
Alongside financial tools, new public bodies have been formed to coordinate delivery. A government-sponsored organisation established in 2026 to accelerate projects—initially called Great British Nuclear—was renamed Great British Energy – Nuclear in June 2026. These entities are intended to help shepherd projects from planning through to construction and operation, supporting the broader target of substantially increasing nuclear capacity.
Context within the wider electricity system
At the end of 2026 the United Kingdom’s total generation mix was diverse: natural gas and wind were both significant contributors, with nuclear providing an important, low-carbon baseload. Total electricity generation was about 285 TWh, while installed capacity across technologies reached roughly 105 GWe. These figures illustrate why policymakers view an expanded nuclear sector as complementary to renewables when planning a reliable, decarbonised system.
Expanding nuclear output involves complex trade-offs: managing ageing plant retirements, securing investment in new builds, finalising licensing for novel technologies and integrating large and small reactors into a grid already adapting to rapidly growing variable renewables. The UK’s approach combines regulatory reform, selective funding models and targeted institutional support to address those challenges while staying aligned with long-term climate obligations.
