ESB workers have approved a package that will cut 1,000 jobs, most of them before the end of the year.
More than 6,000 staff were balloted on the voluntary severance scheme, which will cut payroll costs by €140m over four years.
Two-thirds of staff voted in favour of the deal, which includes 700 voluntary redundancies and a further 300 due to retire by 2015 who will not be replaced.
The package also includes cuts in lump-sum payments, overtime, subsistence, expenses and the end of performance- related pay for staff, managers and executives.
Basic pay, which is around €70,000 a year, will be protected.
There will also be a pay freeze and a cap on profit-sharing payments, but staff will continue to be paid increments.
ESB executive director John Campion welcomed the vote, which he said would "ensure that the company can continue to invest in national critical infrastructure while remaining competitive in electricity and gas markets".
He said it involved a package of earnings, reductions and cuts in staff numbers and followed intensive negotiations between ESB management and the Group of Unions.
The new deal will reduce staff numbers from 6,700 to 5,700.
The ballot had been due to take place two weeks earlier but was delayed because of a number of "anomalies" in the balloting arrangements.
Some ballot papers were sent to staff who had already taken voluntary redundancy.
The voluntary severance scheme opens from today and staff have until the end of May to decide. The approvals will be issued by the end of July.
Staff whose applications are successful will have to leave the company before the end of the year and cannot be re-employed.
Workers aged between 50 and 60 years will have their pension benefits, including lump sums, deferred until they reach 65. They will get a severance payment up-front on a sliding scale, depending on their length of service.
The latest scheme is not as attractive as a previous scheme where workers were allowed to opt for half-pay for about 10 years until they drew down their pensions.
The ESB says the payroll cuts are part of a wider cost-reduction programme within the company which will reduce overall costs by €280m over the next four years.