Northern Ireland electricity supplier, Share Energy, is to increase its tariff prices by 12.6% from 1 October.
The supplier said the industry has faced "exceptional volatility" following Russia's invasion of Ukraine and instability in the Middle East.
The company entered Northern Ireland's electricity market in 2004.
Its CEO Damian Wilson said it "isn't a decision we've taken lightly" and has called on the government to address the Northern Ireland electricity sector's over-reliance on gas.
The Consumer Council for Northern Ireland has said the supplier's credit customers and prepayment customers will see their annual electricity costs rise by about £129 a year.