Electric Ireland has announced plans to withdraw from the residential market in the north.
The ESB-owned supplier has around 53,000 residential customers in Northern Ireland.
The company said the decision follows a strategic review of its business.
In a statement, Electric Ireland said: “As a result of this review, we will be focussing exclusively on the business market and, over time, our intention is to no longer serve the residential market.”
The supplier first entered the northern market in 2000, focusing primarily on business customers.
It currently has a 35% share of the business electricity market in Northern Ireland.
Electric Ireland entered the domestic market in the north during 2015.
It became the north’s third largest supplier of electricity to households, with a customer base of more than 100,000.
But it has lost a significant number of those domestic customers in recent years.
Its 53,000 residential customers currently represents just a 6% share of the northern market.
The ESB Group’s presence in the north includes six wind farms and a gas-fired power station at Coolkeeragh in Derry.
A spokesperson for the supplier said it will continue to supply and support residential customers during the transition.
“This will involve working collaboratively with key stakeholders, including the Utility Regulator, and with our residential customers to ensure a managed approach.
“During the process, Electric Ireland will continue to supply our 53,000 residential customers.
“We understand and appreciate that this news may be unsettling for some customers and so it is important to stress that there is no immediate change.
“There will be no interruption in supply to Electric Ireland customers and they do not need to take any action. Electric Ireland will contact them directly in due course.”
Industry body Manufacturing NI said it received assurances from Electric Ireland and ESB that their contracts with non-domestic customers will continue as normal, with no plans to exit the business market.
Electric Ireland is currently under formal investigation by the Utility Regulator regarding eight potential breaches of its licence.
The nature of the alleged breaches remains unclear.
Last year a technical fault affected thousands of Electric Ireland customers, leaving some without power.
It mainly impacted customers using keypad meters.
The north’s regulator can impose fines where it concludes a company breached the terms of its licence.
Failure to comply with enforcement action can result in suppliers being stripped of their operating licence.
A previous investigation by the Utility Regulator led to Electric Ireland paying £250,000 to charities in 2020.