Nuclear energy has moved from the margins of UK energy policy back to its centre. After years in which new nuclear was treated as too expensive, too slow, and too politically difficult, it is now part of the government’s core thinking on energy security, decarbonisation, and industrial strategy. Much of that renewed focus falls on a technology called the Small Modular Reactor. The term gets used loosely, so it is worth understanding what it actually means.
What Is a Small Modular Reactor?
A Small Modular Reactor is a nuclear power station. It generates electricity through nuclear fission, the same process that has powered large reactors for decades. What distinguishes it is scale and construction method.
Traditional large nuclear plants, Hinkley Point C being the most prominent current example, are enormous, bespoke civil engineering programmes. They are built largely on site, take well over a decade to complete, and cost tens of billions of pounds. Each one is, in effect, designed and constructed from scratch.
An SMR is smaller, typically generating up to around 300MW, although Rolls-Royce’s UK design targets approximately 470MW. The “modular” part refers to the intention that major components are factory-manufactured and transported to site for assembly rather than built entirely in place. Once the first unit is complete and the production process is established, subsequent units should be faster, cheaper, and lower risk. The logic is the same as any other manufactured product: unit costs fall as volume increases.
To put the output in context, a single Rolls-Royce SMR unit would power roughly 450,000 homes.
What SMRs Are Designed to Do
The use cases extend beyond straightforward electricity generation. The primary purpose is clean, reliable, 24-hour baseload power that does not depend on wind or sunshine. But SMRs are also being designed with industrial heat production in mind, which opens applications in hydrogen manufacturing, chemical processing, and heavy industry that currently runs on gas.
For the UK, SMRs are being positioned as a solution to several overlapping problems: reducing dependence on imported gas, providing firm low-carbon power alongside intermittent renewables, supporting industrial decarbonisation, and powering the data centres and AI infrastructure that now represent a fast-growing share of national electricity demand.
Who Is Building Them
The UK’s SMR competition ran for several years and concluded with the selection of Rolls-Royce SMR as the preferred technology in June 2025. In April 2026, the UK Government and Rolls-Royce SMR entered into a formal contract, completing the selection process and moving the programme into its delivery phase.
The first UK deployment is expected at Wylfa in Anglesey, with plans for three units at the site. Government financial backing is substantial: reports cite up to £599 million from the National Wealth Fund and £2.6 billion allocated in the 2025 Spending Review.
Rolls-Royce’s design is based on proven pressurised water reactor technology, the same fundamental physics used in naval nuclear propulsion and conventional large reactors. That gives the engineering a degree of maturity that more experimental reactor concepts cannot claim, even if the factory-build model itself is new.
Globally, other credible programmes include GE Hitachi’s BWRX-300, which is advancing in Canada and attracting interest in Poland; Westinghouse’s AP300, a scaled-down version of its established AP1000 design; and EDF’s Nuward programme in France. NuScale, one of the earliest Western developers, has experienced commercial setbacks due to cost escalation, which is a useful reminder that the technology’s commercial case is still being demonstrated rather than assumed.
What They Will Cost
Cost is the question that cannot yet be answered with confidence. No Western SMR has been built and operated at commercial scale. The first units will be expensive because first-of-a-kind nuclear projects always are. The entire commercial rationale depends on repeat builds: construct ten or twenty units of the same design using the same factory-produced components and the same commissioning procedures, and costs should fall substantially.
GE Hitachi has cited a target of around $2,250 per kilowatt for series production of its BWRX-300, though that figure assumes a mature programme with multiple units behind it. Rolls-Royce has talked about achieving costs competitive with offshore wind over time.
The first UK SMRs will be expensive and heavily supported by public funding. Whether the repeat-build model delivers the projected cost reductions is the defining commercial question for the sector.
When Will They Arrive
The realistic expectation is that the first UK units will not be generating power before the mid-2030s, with independent commentary suggesting later in that decade is more probable. Design finalisation and regulatory licensing will run through the late 2020s, first construction mobilisation is likely around 2029 to 2032, and first generation from 2033 to 2036 depending on how the programme progresses.
That timeline means SMRs are a medium-term solution. The grid pressures the UK faces today, and the electricity demand being created right now by AI infrastructure, will need to be addressed through other means first.
Why This Matters Beyond the Energy Numbers
The SMR programme represents a commitment to rebuilding the UK’s nuclear industrial capability: the engineering skills, the supply chain, the regulatory infrastructure, and the workforce capacity that were largely allowed to atrophy after the last generation of UK nuclear stations was completed.
That rebuilding is already underway at Hinkley Point C and Sizewell C. SMRs, if the programme proceeds as planned, would extend it well into the 2040s and potentially establish the UK as a competitive nuclear exporter. That ambition would have seemed implausible a decade ago. It now has government support, commercial contracts behind it, and a more credible delivery path than at any point in recent memory.
