EDF has estimated that Hinkley Point C could cost up to £46bn and take another four years to complete.
The French state-owned client said that the first reactor will not be in use until at least 2029, two years later than the most recent 2027 goal, and could take until 2031 if electromechanical work runs into problems.
Hinkley Point C, the UK’s first nuclear plant in more than two decades, was estimated to cost between £25bn and £26bn in 2015 (between £33bn and £34.3bn in 2023 prices adjusted for inflation).
The projected cost is now between £31bn and £35bn in 2015 figures and up to £46bn in today’s money, according to the Bank of England inflation calculator.
In a letter to staff, managing director Stuart Crooks wrote: “Going first to restart the nuclear construction industry in Britain after a 20-year pause has been hard.
“Relearning nuclear skills, creating a new supply chain and training a workforce has been an immense task which others will benefit from for decades to come.
“Like other major infrastructure projects, we have found civil construction slower than we hoped and faced inflation, labour and material shortages, on top of Covid and Brexit disruption.”
He also said that 7,000 changes had to be made to the design of the EPR reactors to meet British regulations, requiring 35 per cent more steel and 25 per cent more concrete.
He added: “The energy crisis and the urgent need to fight climate change shows how important Hinkley Point C is. We are determined to get on with the job to deliver a high-quality plant that will serve Britain reliably into the next century.”
EDF warned last February that construction costs might reach up to £32.7b in 2015 figures, but still expected the plant to start generating electricity in 2027. The firm signalled in a presentation to investors a few months later that the project risked further delays.
The project is now past the halfway point, after the dome was lifted onto the first reactor last December. Mechanical, electrical and heating work is set to ramp up this year, quadrupling the number of workers.
When in use, Hinkley Point C will generate around 7 per cent of the UK’s energy consumption.
A Department for Energy Security and Net Zero spokesperson said: “Hinkley Point C is not a government project and so any additional costs or schedule overruns are the responsibility of EDF and its partners and will in no way fall on taxpayers.
“We’ve ended the stop-start approach to nuclear and recently launched a roadmap setting out the biggest expansion of nuclear in 70 years, simplifying regulation and shortening the process for building new power stations – meaning cleaner, cheaper and more secure energy in the long-term.”