Workers at electricity provider Ausgrid will begin stoppages from next month with wage negotiations with the company stalling.
Ausgrid and Endeavour Energy staff will hold a four-hour stoppage on March 3, the Electrical Trades Union says.
ETU secretary Steve Butler said on Thursday the action would involve thousands of workers who operate and maintain the electricity network in Sydney, the Hunter Valley, Newcastle, the Central Coast, Wollongong, the Illawarra, Blue Mountains and parts of the Central West.
"We have said all along that industrial action is an absolute last resort," he said.
"Power workers have been given no choice but to take this action after the NSW government and management at Ausgrid and Endeavour Energy refused to agree to maintaining protections that prevent forced redundancies."
Comment has been sought from Ausgrid.