"Sonia has made an enormous contribution to Ofgem over the last nine years," the regulator's managing director Steve Smith said.
"She has been at the heart of many of Ofgem's most significant achievements including NETA, the major reform of the electricity market, and overseeing the restructuring of the gas market after National Grid decided to sell of four of its regional gas companies.
"In addition to this she has led Ofgem's work with customers and suppliers through two difficult winters and has recently driven forward our thinking and work on sustainability and Europe."
Yesterday Ofgem announced that it had appointed Steve Smith as new managing director of networks to take over from the departing David Grey. Steve Smith is currently managing director of markets.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.