The review of the costs and timetable of the HPC project, concluded that project completion costs are now estimated at £19.6bn, an increase of £ 1.5bn (or 8.3%) on the previous estimate of £18.1bn.
Prices are 2015 values and based on an assumed exchange rate of £1 = €1.23.
The review was undertaken after EDF's final investment decision in September 2016, in conjunction with the project company (NNB) teams.
It also found that the project could fall up to 15 months behind programme.
“The estimated additional costs result mainly from a better understanding of the design adaptated to the requirements of the British regulators, the volume and sequencing of work on site and the gradual implementation of supplier contracts,” EDF said.
EDF's projected rate of return (IRR) is now estimated at about 8.5% compared to about 9% initially.