The first of two nuclear reactors at the Vogtle nuclear power station near Augusta might not begin generating electricity until as late as March 2023 and the reactors will cost their owners nearly $30bn, Georgia Power said.

Southern Company, the Atlanta-based parent of the Georgia utility, made the announcements as it released its annual earnings.

When approved in 2012, the two AP1000 reactors were estimated to cost $14bn, with the first electricity being generated in 2016.