UK Puts Sizewell B on a Fixed-Price Contract, Extending Its Life to 2055
EDF's 1.2 GW plant becomes the first British reactor on a CfD, a funding u-turn that keeps 3% of national supply running for two more decades.
The UK government has agreed with EDF to extend the operating life of the 1.2 GW Sizewell B nuclear station by 20 years to 2055, a deal it says will bolster energy security and lower long-term electricity costs.5 It is the first British nuclear plant to be handed a contract for difference, the fixed-price mechanism used until now for new build and renewables, in what Energy Voice described as a government u-turn on how existing reactors are funded.4
That reframes the economics of Britain's ageing fleet. Sizewell B currently supplies around 3% of the country's electricity, enough to power roughly 2.5 million homes, and keeping it on the system to mid-century removes a chunk of firm low-carbon supply that would otherwise have retired.5 A CfD gives EDF a guaranteed price per megawatt-hour rather than exposure to wholesale power, shifting price risk onto consumers in exchange for a longer commitment.4
The trigger was political. Energy Voice tied the decision directly to the energy price shocks that followed the war on Iran, and Chancellor Rachel Reeves called the project a vital part of Britain's energy plans.4 After the volatility of the past year, a two-decade extension on an existing, paid-for asset is among the cheapest firm capacity a government can secure.
Cheaper, at least, than the alternative. The extension lands as Britain's flagship new build, the 3.2 GW Sizewell C, absorbs mounting cost pressure. The government's spending watchdog found the plant could save consumers GBP 18bn on energy bills but warned the benefits would not outweigh costs until 2064, with significant uncertainties still attached.1 EDF added a projected £2.16bn to the bill in February (2026-02), the latest in a series of delays and increases.2
The contrast is the point. Extending a running reactor for 20 years is a known quantity; building 3.2 GW of new capacity at a headline cost of around £48bn is not.3 Sir Geoffrey Clifton-Brown, who chairs the public accounts committee overseeing the National Audit Office, warned that Sizewell C is a project of exceptional scale, complexity and significance for taxpayers.2 The government still expects the new plant to deliver up to 3.2 GW, powering as many as 6 million homes and providing around £2bn a year in electricity-system savings versus other low-carbon options once running.2
Behind both decisions sits an ageing fleet running out of road. EDF's Torness plant in East Lothian was recently granted a stay of execution to 2030, backed by a £1.3bn investment pledge from the French firm.3 Energy Secretary Ed Miliband has commissioned Great British Energy-Nuclear to assess Scotland's potential for new capacity, framing the push as a nuclear golden age even as the Scottish government stays opposed.3 Extending Sizewell B buys time while that longer pipeline is negotiated.3
For power markets, the near-term read is modest. Sizewell B was already generating; the deal changes when it stops, not what it produces now.5 Keeping 1.2 GW of nuclear on the grid to 2055 trims the volume of gas-fired generation Britain will lean on over that horizon, but the effect is spread across decades rather than felt in any single delivery period.5
The unresolved number is the strike price. Neither the CfD level EDF secured nor the mechanism for passing its cost to bills has been disclosed, and that figure decides whether the deal genuinely lowers long-term costs or simply relocates them onto consumer levies.4 Watch, too, for read-across to the rest of the fleet: if a fixed-price contract becomes the template for keeping old reactors open, EDF's other stations become candidates for the same treatment.4 The precedent set here may matter more than the megawatts.