As projected costs for the new nuclear power station at Hinkley Point C rise to an estimated £40bn, France’s finance audit institution Cour des Comptes has just told EDF, a state-owned corporation, to reconsider backing the proposed new reactor build at Sizewell C.

With £2.5bn already spent and £5.5bn authorised by the UK government, and an estimated £700mn invested by EDF, the European Pressurised Water Reactor (EPR) nuclear reactor development costs at Sizewell C already outweigh the total original project budget even before construction starts, according to reports. The UK government and EDF maintain that Sizewell C will cost around £20bn, though £8.5bn will have already been spent ‘in development’.

Simultaneously, based on future power prices, the French auditor predicts only ‘mediocre profitability’ for the recently launched EPR reactor at Flamanville, according to Reuters, and suggests EDF limits its financial exposure to Hinkley C.

These numbers carry meaning.

Time out
The choices we make will determine the success or failure of our climate actions. Cost is key, but time is the most relevant variable – and time is running out. It’s worth recalling that global data analysis by the UK government reveals that construction of just one new nuclear station typically takes between 13 and 17 years. In comparison, global new solar generation capacity was deployed 100 times faster than net new nuclear in 2024, and new wind 25 times faster, says a report in pv magazine.

Due to shorter timelines and lower costs, renewables are now 10 times more effective at cutting CO₂ emissions than nuclear, reports the Intergovernmental Panel on Climate Change. It adds that accelerating renewables coupled with energy efficiency is the most efficient way to reduce global emissions by 2030. Note that, given current trajectories, renewables plus energy efficiency will be even more productive than new nuclear by that date, and after.

China alone has 180 GW of utility-scale solar power under construction and 159 GW of wind power, bringing its total wind and solar power under construction to 339 GW, according to a report in The Guardian. (Its nuclear newbuild programme amounts to 30 GW, according to the World Nuclear Association.)

With global annual renewable capacity additions rising from 666 GW in 2024 to almost 935 GW in 2030, the International Energy Agency concurs that renewables will do the heavy lifting for the energy transition. In comparison, nuclear’s share of global electricity production almost halved from 1996 to 2023 – largely due to the high costs of, and delays to, building and operating nuclear reactors.

Far from improving, the latest reactor designs offer the worst-ever record of delays and cost escalation.

The choices we make will determine the success or failure of our climate actions – cost is key, but time is the most relevant variable, and time is running out.

Meanwhile, the UK Institution of Mechanical Engineers has stated that UK coastal nuclear sites will need ‘considerable investment’ to try to protect them from rising sea levels, and even ‘relocation or abandonment’. In other words, nuclear seems to be on the front line of climate change, and not necessarily in a good way. Existing and proposed new coastal reactors – together with their spent nuclear fuel and radioactive waste stores – seem to be increasingly vulnerable to ramping sea-level rise driven by storm surge flooding, and to ‘nuclear islanding’, where the plant is surrounded by water.

Small is the new big
Because of the significant costs of, and delays to, large nuclear reactors, industry emphasis has moved to small modular reactors (SMRs) – despite these sharing similar cost, delay, safety, security and waste problems. So far, due to ramping cost over-runs, several key SMR projects have fallen by the wayside.

In the UK, Rolls-Royce has tried to resolve lost economies of scale by designing an SMR that isn’t actually an SMR. While the International Atomic Energy Authority defines SMRs at maximum 300 MW power output, Rolls-Royce’s effort comes in at 470 MW – about the same size as the early Magnox reactors, half the size of the current workhorse French nuclear fleet reactors, and one-third the size of the vast EPR reactor in construction at Hinkley Point C.

So what
As to the end-game argument for new fission power – as back-up to variable renewables – nuclear is designed for baseload and attempts at load-following make the industry’s economic case profoundly more problematic. You can’t have your cake and eat it. And whilst not diminishing the problem of Dunkelflaute, rather than throwing vast resources at very late nuclear, there are evolving and well-practiced energy storage solutions to cope with and resolve any potential for a few hundred hours per year of low wind combined with low solar.

We need to secure clean, safe, affordable, sustainable, low-carbon energy to power industry, transport, homes and businesses. Instead of pursuing an expensive non-renewable technology, our resources should be channelled into realistic solutions that work: the expansion of renewables across all sectors, grid modernisation, storage, interconnection, energy efficiency and demand-side management.

The views and opinions expressed in this article are strictly those of the author only and are not necessarily given or endorsed by or on behalf of the Energy Institute.

• Further reading: ‘How nuclear and renewable energy could work together in the UK’. Nuclear reactors could generate useful heat and produce green hydrogen as well as electricity – and thus play a major role in decarbonisation efforts – if the role of civil nuclear power in the energy mix could be reconsidered. Professor Zara Hodgson, Director of the Dalton Nuclear Institute at the University of Manchester, explains how.
• Following Europe’s recent energy security crisis and the expectation of increased industry energy demand, plus the climate emergency, the light is once again shining on civil nuclear power. As a result, some of long-standing barriers to finance have shifted, which might help facilitate newbuild civil nuclear power projects.