Mr Dowling (66), told the Otago Daily Times he would finish working for the company at the end of September.
His job was already being advertised, with applications scheduled to close on May 21.
Mr Dowling, of Clyde, was appointed chief executive in 1999 when Pioneer Generation was formed after the sale of Central Electric Ltd's retail and lines businesses.
Proceeds from the sales were transferred into the Central Lakes Trust, which owns Pioneer Generation.
Mr Dowling had worked with Central Electric since 1996.
He and his wife Janine moved to Central Otago from Dunedin in 1987.
Mr Dowling, originally from the United Kingdom, said he was "a bit undecided" about his future.
He would wait until his wife finished a degree at the University of Otago before making any major decisions.
"It depends where we end up after that.
"We've got a trip planned and we'll take it from there once we get back," he said.
Mr Dowling said he had experienced "a lot of highs" during his time as chief executive of Pioneer Generation, including the development of a small wind farm at the company's Horseshoe Bend hydro-electric power station near Roxburgh.
"It's been a great job, a great team of people I work with.
"Commissioning new power stations and getting the first wind farm up and running have been among the high points," he said.
As an electricity wholesaler, Pioneer Generation supplies power through local networks and the national grid from its 12 power stations throughout Central Otago and Southland.
