The company said staff had been told about the cuts, which were part of its “ongoing transformation.”
A spokesman said: “This difficult decision was made because we need to respond to the growing challenges we face. The energy market is going through continued rapid change, competition is fierce, our energy customers are leaving us and we’re operating under a price cap.
“Over the next 45 days, as part of a full consultation process, we will discuss the proposals and seek the views of employees and their representatives.”
Unions said the job losses were a “terrible blow” for the workforce.