Bríd Horan has been appointed as deputy chief executive of ESB, replacing John Shine who is set to take up a role at Eircom in August.
Ms Horan joined ESB in 1997 and has worked in a number of divisions in the company, most recently as executive director of ESB Business Service Centre and Electric Ireland.
Before joining ESB she worked in Pension and Actuarial Consulting at KPMG.
Mr Shine, who has worked with ESB for 31 years, has been appointed managing director of Eircom's Network division.
ESB CEO Pat O’Doherty described Ms Horan as “a very experienced and valued member of ESB’s leadership team”.
She comes to the role “at a time of great change and uncertainty” in the sector, he said, as they seek to deal with energy affordability, security and pollution concerns.
Mr O’Doherty also praised Mr Shine, saying he was “instrumental in driving forward major investments” over the years.