Hinkley C nuclear plant costs could soar to £46bn

The final cost of the Hinkley Point C nuclear plant being built in Somerset may soar by about a third, according to the French firm developing it.

The completion date could also be delayed by three years.

In 2022, the cost of the UK's first new nuclear plant since the 1990s was estimated at £26bn, with a target date for completion of June 2027.

EDF now estimates that the cost could hit £46bn, when taking price rises into account.

Previous cost estimates have been expressed in 2015 prices for easy comparison over time.

But taking inflation into account, the previous estimate on final costs of £26bn works out at £34bn today. The updated estimate of £31-35bn, could see costs hit £46bn in today's prices - an increase of about a third.

In a letter to staff, seen by the BBC, Stuart Crooks, the managing director of Hinkley Point C, said substantial design changes, required by British regulations, meant there were 7,000 changes that needed to be made to the site, with 35% more steel and 25% more concrete needed than originally planned.

UK bill payers will not be directly affected by those building cost and time overruns at Hinkley Point as EDF agreed to shoulder the risk on the project in return for an agreed electricity price that was substantially higher than the average price in 2015 and would only rise in line with inflation.

However, this price shock comes at a sensitive time for the UK government, which has agreed to allow construction costs for a new plant at Sizewell in Suffolk to be added to customers' bills gradually over the decade which it will take to build.

The government has also just doubled its own investment into Sizewell C to £2.5bn and is in the process of raising capital from private investors.

Last week, the government triggered a "development consent order" that allows early-stage construction to begin in Suffolk despite several legal challenges from local and national opponents who have taken their fight to the Supreme Court.

Alison Downes from campaign group Together Against Sizewell C said said that the announcement of additional funding was"inexplicable" following news of delays to one of the government's key nuclear projects.

She described the Hinkley and Sizewell projects as an "unmitigated disaster".

"The government should cancel Sizewell C instead of handing over scarce billions that could be used instead for renewables, energy efficiency or - in this [general] election year - schools and hospitals," she added.

The BBC has approached the Department for Energy Security and Net Zero for comment.