Mr Costello would leave ActewAGL in October with general manager Tania Hutchison to be acting executive until Mr Knox took up the role in November.

Mr Costello held the chief executive position at the utility company for 10 years before announcing his retirement in May.

ActewAGL chair Paul Adams said Mr Knox had an extensive business knowledge, energetic leadership and understood the challenges the company faced in the future.

“I consider myself to be very fortunate to have the opportunity to lead ActewAGL through an exciting new phase,” Mr Knox added.