The independent expert group on pylons says it will need at least six months to say whether one major power line should be put underground.
The expert group says it expects to issue an opinion on the Grid West project linking Mayo and Roscommon by January.
However, it says it won't have a ruling on the Grid Link project joining Cork and Kildare until the end of July 2015.
The expert panel also says it is considered the decision-making process for the interconnector between Meath and Tyrone, and says the same standards were applied to that process as to the other two projects.