Sizewell C Cost Doubles to £35bn as Watchdog Says Benefits Won't Land Until 2064

Sizewell C Cost Doubles to £35bn as Watchdog Says Benefits Won't Land Until 2064 Britain's flagship nuclear plant faces mounting scrutiny after its price tag nearly doubled, with the watchdog warning consumers won't see net benefits for four decades. The bill for Sizewell C has grown to around £35 billion, almost double the £18 billion estimate from 2016, after the project developer announced in February a further £2.16 billion increase to projected costs.⁴ The plant, designed to add 3.2 GW of capacity to the British grid and supply electricity to up to six million homes, is shaping up as one of the most expensive infrastructure commitments in UK history.⁴ That matters because the spending watchdog has now put a number on the gap between promise and payoff. The National Audit Office concluded the project could save consumers £18 billion on energy bills over its lifetime, but warned that net benefits would not outweigh costs until 2064, Montel reported.¹ For a project seeking public backing and private financing in the current environment, a 38-year payback horizon is a difficult sell.¹ Sir Geoffrey Clifton-Brown, chair of the public accounts committee, was blunt. "Sizewell C is a project of exceptional scale, complexity and significance for taxpayers," he said, according to OilPrice.com, adding that experience with similar projects warranted serious caution.⁴ The government's formal position remains supportive. Ministers say the plant could deliver around £2 billion a year in savings from the electricity system compared to relying on other low-carbon technologies.⁴ The final investment decision to proceed was confirmed, with total project cost now cited at approximately £38 billion in development terms.² But the gap between ministerial projections and the NAO's timeline for when savings materialise points to a forecast built on assumptions that will take decades to test. The project has already experienced a pattern of delays and cost increases before a single concrete pour. The most recent addition, the £2.16 billion revision announced in February, brought the running total close to double the original estimate.⁴ A project that has reached this cost trajectory at the planning stage carries obvious risk of further slippage once construction begins in earnest. Sizewell C sits alongside a separate programme to develop small modular reactors. The government pledged £2.5 billion for SMR development and selected a site on the Isle of Anglesey in north Wales for the UK's first such facility.³ The broader intent is energy security through diversification away from fossil fuels, but whether a single project at this cost and on this timeline is the right vehicle for that goal is a question the NAO's numbers make harder to answer.⁴ The NAO's 2064 breakeven date is presumably a base case; any schedule slippage pushes it further out.¹ The 38-year gap between outlay and net benefit creates a financing challenge that ministerial confidence alone will not resolve.¹ The government's assertion of £2 billion a year in system savings sets up a very long test of whether that figure survives contact with actual construction timelines.⁴ The next substantive signal to watch is whether Sizewell C secures the private financing it needs alongside government support. A commitment of approximately £38 billion, with the spending watchdog formally questioning its value trajectory, will face hard questions from any institutional investor.⁴ Cost developments in the coming quarters, and progress at the planning and procurement stages, will set the tone for how the market prices execution risk on a project of this scale.^4,1