Mr Graham, 66, is currently chief executive of Networks NSW, the state-owned manager of electricity distributions businesses Ausgrid, Endeavour Energy and Essential Energy.

But he has also served as chief operating officer of the State Rail Authority, managing director of National Rail Corporation and chief executive of RailCorp since he first joined the public service in 1969 as a civil engineer for the NSW Railways.

Mr Graham's retirement coincides with the winding up of Networks NSW in light of the partial privatisation of Ausgrid and Endeavour by the Baird government.

Most recently, Mr Graham has been locked in negotiations with unions over redundancies in the face of the national energy regulator's decision to slash the amount of revenue that can be charged by electricity companies.

"It has been a privilege to serve the people of NSW for all of my working life," Mr Graham said in a statement on Wednesday.

"I am particularly grateful for the support of my family. I also want to pay tribute to the many dedicated employees I have worked with over my career who have embraced the difficult challenges of an ever-changing economy and technology."

Networks NSW chairman Roger Massy-Greene said Mr Graham would retire on December 31 after almost 47 years of service to NSW and paid tribute to him as "an exceptional leader".

"I want to thank him for his sustained commitment and outstanding contributions to worker and public safety, and to improved customer outcomes through lower costs and continued reliability," he said

Mr Massy-Greene said that after Mr Graham's retirement, the deputy CEOs of Ausgrid and Endeavour Energy, Trevor Armstrong and Rod Howard, would be appointed acting chief executives pending the finalisation of the partial privatisations.