Peter Haigh, the managing director of Bristol Energy, has left the council-owned organisation.
Haigh, who helped launch the company in 2015, will be replaced by Bristol Energy’s finance director Marek Majewicz as interim managing director.
Haigh stepped down from Bristol Energy before Christmas. He said: “I’d like to thank all the staff whose passion and commitment have helped us through every step of our journey so far.
“They have ensured that our founding principle of being a force for social good remains at the heart of everything we do.”
The energy company currently supplies 76,000 homes and 2,500 businesses.
Bristol City Council’s deputy mayor Craig Cheney said: “I would like to thank Peter for all he has done in establishing Bristol Energy and getting the business to where it is today.
“The performance of the business reflects the hard work and dedication of Peter and his team, the company having hit key milestones in a particularly difficult energy market.
“We wish Peter all the very best for the future.”
In August Bristol Energy announced it was increasing its standard variable tariff (SVT) for the first time in its history due to “increased uncertainty”.
The company blamed rising wholesale energy prices for the 12.6 per cent increase.