Thousands of Ausgrid electricity workers in New South Wales have voted to strike next month in the peak of summer heat after negotiations over pay and career progression soured.

The Electrical Trades Union says after more than three years of pay freezes along with nearly 2,000 job losses during the same period, workers at the electricity network have no choice but to take action. Workers are seeking a pay rise of 3% a year.

“During this same time, Ausgrid executives awarded themselves pay increases averaging 5.3% a year, while they also enjoyed average bonuses of more than $50,000 each in 2014, 2015 and 2016,” ETU organiser Mark Buttigieg said in a statement on Thursday.

More than 93% of about 2,800 Ausgrid members, made up of four unions, supported industrial action including work stoppages, refusing to do overtime and callouts.

Workers will decide on what specific actions to take on 31 January.

Ausgrid delivers electricity to more than 1.7 million homes and businesses in NSW across Sydney, the central coast and the Hunter regions.

In an official statement, Ausgrid, which is jointly owned by the NSW government, Australian Super and IFM Investors, said it was “disappointed” at the proposed union action.

“We believe we have achieved in principle agreement on virtually all of our proposal,” the Ausgrid CEO, Richard Gross, said in a statement. “If the unions elect to take industrial action, Ausgrid will ensure there is minimal impact on energy supply to our customers.”