Ofgem chief executive Jonathan Brearley (pictured) will step down at the end of March to become permanent secretary at the UK Department for Energy Security and Net Zero.
The Gas and Electricity Markets Authority said the board will begin a formal search process to appoint a permanent successor.
The regulator added that Tim Jarvis, currently director general for markets, will serve as acting chief executive during the transition period.
Brearley has led Ofgem through a period that included the Covid pandemic and the gas crisis.
The regulator said his tenure included work to stabilise the energy market, reform financial resilience in the retail sector and improve consumer satisfaction.
Ofgem added that Brearley also drove regulatory reforms linked to infrastructure development and initiatives including the Accelerated Strategic Transmission Investment programme and the creation of NESO.
“On behalf of the Board, I want to thank Jonathan for his immense dedication and service,” said Gas and Electricity Markets Authority and Ofgem chair Mark McAllister.
“We wish Jonathan the very best in this next chapter and look forward to continuing to work together as we deliver a successful energy transition for consumers.”
“It has been a privilege to lead Ofgem and work alongside such a talented group of public servants,” said Brearley.
“I am confident that Ofgem is in excellent hands with Tim alongside the wider executive committee and well-positioned to continue delivering on its mission to protect energy consumers now and into the future, as we advance through the energy transition.”