Power plants, multinational companies and building works across the country could be brought to a standstill within weeks as electricians backed an indefinite strike.
The Technical Engineering and Electrical Union (TEEU) said the industry-wide action will begin on Monday February 24 in a row over pay.
Eamon Devoy, the union's general secretary, said 94% backing for a mass walk-out among its members demonstrated the strength of feeling over wage rates.
"During the last nine years they have been faced with serious austerity measures including both direct and indirect tax increases, negative equity in their homes and loss of medical insurance as well as falling earnings," he said.
"Now, just as the economy shows signs of recovery, the employers want to impose pay cuts."
The TEEU has accused employers of threatening a 10% reduction in pay, down from the existing hourly rate of 21.49 euro to 19.34 euro.
Under previous arrangements, including historic employment deals abolished last year by the Supreme Court and Labour Court recommendations, electricians should be getting 24.78 euro an hour from April this year, the union has argued.
It has tried to reach agreement with employers about pay, but a lack of consensus was now endangering customer and safety standards, the TEEU has claimed.
"It is in no-one's interest that this should happen except for a few cowboy operators whose only interest is in winning a quick buck and moving on to rip off the next customer," said Mr Devoy.
The indefinite strike action will be taken "nationally against all employers simultaneously or strategically against individual employers" in a plan yet to be agreed by the union, he said.
The TEEU said it has previously brought manufacturing and construction to a standstill with industrial action.
Business leaders have attacked the threatened action as damaging and warned it will wreak major disruption to the entire economy.
Maeve McElwee of Ibec, which represents employers, demanded the union immediately withdraw the strike notice, which was served this morning.
"The strike threat is damaging and unwarranted," she said. "Established processes exist to deal with disputes and these should be used."
Ibec said calls for a 4.9% pay rise from electricians were extraordinary at a time when construction remains depressed and companies are struggling.
"The focus should be on creating jobs and protecting existing employment," she said.
"The expectations being created by the TEEU are unrealistic and damaging to the sector."