The distribution network operator said Emery had made the decision for personal reasons and that he would continue in the role until his successor is appointed.
Having joined ENW in 2016, Emery’s previous roles include as group operations director at Drax and as refinery operations manager at multinational oil and gas company Exxon Mobil.
The ENW board thanked Emery for his “outstanding leadership of the company, and for his extraordinary contribution during a period of significant evolution in this industry”.
Alistair Buchanan, chairman of ENW, said: “Pete has contributed immensely to the success of the organisation over the past six years.
“He has led the business into developing a comprehensive business plan for 2023-28 that will help the North West meet its target of achieving net zero. His leadership will be greatly missed.”
ENW said it aims to complete the search for the new chief executive by the end of the year.