EirGrid has scrapped plans for a massive high-voltage overhead power line running across six counties and there are major doubts about a second pylon project.
The company has announced that the Grid Link project between Cork and Kildare will not go ahead, and revealed that a second scheme called Grid West will only proceed if a large-scale wind farm in the west secures planning permission.
Chief executive Fintan Slye said the case for building the 100km Grid West line would change if a 112-turbine Oweninny wind farm planned for Bellacorick in Co Mayo was refused permission.
The €600m renewable energy project, proposed by the ESB and Bord na Móna, is currently with An Bord Pleanála and a decision is expected later this year.
Mr Slye's comments came as EirGrid revealed that new technology would be used to bolster existing lines running between Cork and Kildare via Wexford.
It had been proposed to erect high-voltage power lines, or install the lines underground, as part of the controversial Grid Link project, but these options have now been ruled out.
There was vehement local opposition to the 400kV scheme, but earlier this year EirGrid revealed a so-called "regional option", which involves using technology called "series compensation" to allow more power to flow through existing lines.
The company has now decided to pursue this option, which will cater for the region until at least 2030. There will be consultation with affected communities prior to works commencing.
"The regional option effectively negated the need for new infrastructure," Mr Slye said. "There is no requirement to proceed with overhead lines. We will be moving ahead to deliver what I believe is a better option for all concerned.
"In 2008, which this project was proposed, it was based on Celtic Tiger growth rates. Demand has dropped, this (option) would not have been feasible in the past. One of the key things we learned was we would need to do a detailed analysis of the options."
Some upgrade works of existing structures will be required, including 110kV overhead lines between Kilkenny and Wexford via Great Island, while a new 400kV circuit between Moneypoint in Clare and Kilpaddoge in Kerry will be constructed across the Shannon estuary.
The works will cost €156.8m and take four years to complete. The cost of undergrounding power lines for Grid Link was put at €643m, and at €215m if it was erected on pylons.
The Grid Link Action Group said it was "very pleased" with EirGrid's decision, and called on the Department of the Environment to publish planning guidelines for pylon projects and address health concerns.
"We have questioned the need for the project and asked had all options been considered. It is clear that EirGrid did not give adequate consideration (to the regional option)," spokeswoman Maura Leigh said.
The decision to review the available options came after EirGrid announced late last year that it would improve its public consultation process. It came after chairman John O'Connor admitted that he would not like to live close to a pylon.
A third controversial grid project, the €283m North South Interconnector between Tyrone and Meath, is in planning.