In February 2025 Stop Sizewell C, with Professor Steve Thomas of Greenwich University Business School and Tom Burke, Founder of E3G, made the following submission to the government’s multi-year Spending Review. For the answers to this question, see below, or read the full submission here: Stop Sizewell C et al Spending Review Submission February 2025

Question 1 – Is it credible that Sizewell C would be built on time, for a fraction of the cost of Hinkley Point C?  

a) Accurate predictions of Sizewell C’s cost given the EPR’s track record are impossible.

No European Pressurised Reactor (EPR) reactor project has ever been completed to budget or on time. All six reactors worldwide have or will cost at least double their expected budgets and have been/are between 6 and 14 years late. The case of Hinkley Point C is especially stark: EDF’s most recent estimates of the construction cost – excluding finance charges – is up to £35bn [2015] – £46bn in 2023 money – almost double its £18bn budget [2015] when the Final Investment Decision (FID) was taken in 2016. These costs do not include financing costs, which EDF has said might double the total construction cost. Completion of Unit 1 at Hinkley Point is now delayed to between 2029 and 2031, 4 to 6 years later than claimed at FID. EDF claims that Hinkley Point C is “First of A Kind”, and that Sizewell C will benefit from replication and “learning” which would reduce construction time and cost, but Hinkley is building the 5th and 6th EPRs globally. 

Sizewell C would be the 7th and 8th EPRs, and almost certainly the last; for its future orders, France will be building a significantly modified design, the EPR2. EDF has made five cost and completion revisions since the Hinkley C FID; the first in 2017, just a year after FID, and a year before construction started. Given the project is only halfway through construction, it is implausible that there will not be further revisions. Taishan I & 2 in China took double the predicted build time and were reportedly 50% over budget. Olkiluoto 3 in Finland was 14 years late and three times over budget, and Olkiluoto 4 was cancelled. Flamanville 3 in France came online (though is not yet up to full power) 12 years behind schedule and four times over budget; £11.2bn [2015] for a single reactor. These repeated failures suggest that learning from previous EPR projects has not happened, and with costs up to £17.5 bn, [also 2015 money], for each of two reactors, the experience of Hinkley Point C suggests that replication has increased cost. 

The only construction cost figure for Sizewell C in the public domain is £20bn, excluding finance charges from May 2020, which is widely held to be unreliable, given that it is only about 40% of the latest cost estimate for Hinkley Point C. A Financial Times report, citing multiple sources, that the project would cost up to £40bn provoked Ministers and Sizewell C executives to say they “do not recognise this figure”, but this response is very different from a statement that it would not cost this much. Stop Sizewell C has its own (different) source that supports the £40bn cost. DESNZ continues to refuse to publish cost estimates or even a target completion date for Sizewell C, citing commercial confidentiality, but this excuse for the headline cost is hard to understand.

b) France won’t build any more EPR(1)s

Given the apparent lack of learning, the more realistic assumption is that the problem lies with the technology, not just the poor execution of Hinkley Point C and the other EPR projects. Former EDF CEO Henri Proglio told the French Assembly in December 2022: “The EPR is too complicated, almost unbuildable.” No amount of replication can render a complex technology simpler. As a result, EDF has announced that France will not build any more of the design used for the existing six EPR orders, and proposed for Sizewell C, but proposes to construct six reactors in France of a modified design, the EPR2, described by EDF as “simplification and optimisation of the design of the EPR”, but forecast cost reductions are at the expense of reduced safety features such as a single rather than a double containment skin.

c) Any replication ‘savings’ would be lost in the complex Sizewell C site. 

The nuclear industry has cited the benefits of replication to save money, but this cannot include the site. Sizewell C’s site has been described by a senior Office for Nuclear Regulation source as “expensive to develop” compared to Hinkley C. The same source has expressed the view that any savings the project might expect to make through above-ground replication are likely to be absorbed by the complex groundworks required at Sizewell. Sizewell is a smaller, more constrained site than HInkley C, geologically different, backed by marshes and adjacent to an internationally renowned nature reserve, with the platform expensively requiring a 60m deep cut off wall to enable dewatering.