The cost of building the new nuclear power station at Hinkley Point has risen by £1.5 billion, it has been announced.
French energy giant EDF said it will now cost £19.6 billion to build the site in Somerset.
The news follows a review of the costs and timetable of the project, undertaken after EDF's final investment decision last September.
A statement said: "The milestone for the first nuclear safety concrete for the building of Unit 1, scheduled for mid-2019, is confirmed, assuming that the final design, which is on a tight schedule, is completed by the end of 2018.
"Project completion costs are now estimated at £19.6 billion in 2015 sterling, an increase of £1.5 billion in 2015 sterling, compared to previous evaluations.
"This estimate includes successful operational action plans, in partnership with suppliers.
"The estimated additional costs result mainly from a better understanding of the design adapted to the requirements of the British regulators, the volume and sequencing of work on site and the gradual implementation of supplier contracts."
EDF said there will be no financial impact on UK consumers of the increased costs.
It added there was a risk of deferral of 15 months for the power station's Unit 1 and nine months for Unit 2, but it was sticking to the objective of 2025 for start-up.