Energy company EDF has announced it is to move to a new site in Gloucestershire as its current premises are too big and not energy efficient.
The company is among the largest employers in the county and is set to move to Gloucester Business Park after 40 years of being based in Barnwood.
Finance director David Tomblin said the firm would look to move next year.
He said its current office could accommodate 2,000 people but only about 1,100 worked there each day.
Mr Tomblin said the plans were in the pipeline before the pandemic but the impact of Covid had spurred the move on.
He said: "Barnwood is too big for us generally.
"It is expensive, but also it is very energy inefficient as you might expect from a 40-year-old building and that's very inconsistent with EDF's net zero ambitions."
EDF announced earlier this year that about 3,000 people would be employed to work on its new nuclear power station being built in Somerset.
Hinkley Point C is set to open in June 2026.