The ESB has agreed to sell assets, including two of its power stations, to a Spanish power company for €450m.
Endesa is buying Tarbert Power Station in Co Kerry and Great Island in Co Wexford.
ESB said talks on issues affecting the 180 workers involved would now start between ESB, unions and Endesa. It said this process was expected to completed by the end of the year.
The process is part of an ESB agreement with the energy regulator to reduce its dominant position in the marketplace.
This is the first time in ESB's history that it has sold operating power stations in Ireland.
For domestic consumers the deal raises the prospect of choice. They could have the option to be billed either by the ESB or Endesa from as early as next year.
Ultimately, Endesa plans to replace both stations with gas power facilities.
ESB is not allowed to increase its capacity in Ireland, so it plans to use the €450m it is making from the deal to invest in Britain.
Meanwhile, ESB says the 180 affected employees will have options. They will be offered alternative positions at the company, a retirement package or to switch their employment to Endesa.
Endesa does not have a supply licence but they do have a generating licence to sell into the grid.
However, the broad understanding is that they are entering the Irish market to supply, as well as generate electricity.
If they were to choose not to supply to homes and businesses they would sell electricity into the grid to be sold on by other power companies.
